Unofficial traditions and customs.
The Corps has many unofficial traditions, promulgated by many Marines and some Marine-based organizations (such as the Marine Corps League, Marine Corps Association, and Young Marines) or media (such as the Marine Corps Gazette, Leatherneck Magazine, or Marine Corps Times).
Nicknames

A recruiting poster makes use of the "Teufel Hunden" nickname.
Marines have been given many generic nicknames:
Devil Dog is oft-disputed term. Most Marines learn that the term comes from "Teufel Hunden", a corrupted version of the German "Teufelshunde" awarded to Marines after the Battle of Belleau Wood. The German high command classified Marines as stormtrooper-quality elite troops. The bulldog has also been closely associated with the Marine Corps as a result, and some units keep one as a mascot.
jarhead has several oft-disputed explanations, to include how the high and tight haircut allows the head to resemble a jar lid and pejoratives about empty heads. However, the term "jarhead" was well established in the 1950s, while the term "high and tight" did not yet exist; Marines who chose to trim their hair closely on the sides were said to have "white sidewalls." Photos of Marines in the World War II era show haircuts that are even longer.
gyrene has dropped out of popular use, and is speculated to be a portmanteau of GI and Marine.
leatherneck refers to a leather collar that was formerly part of the Marine uniform during the Revolutionary War period.

Mottos and battle cries.

oorah is a common battle cry among Marines, being similar in function and purpose to the Army's hooah and the Navy's hooyah cries (to include an affirmative, a display of enthusiasm, and a greeting). Many possible etymologies have been offered for the term.
Semper Fi, Mac was a common form of greeting in times past.
Gung-ho became a common slogan
Improvise, Adapt and Overcome has become an adopted mantra in many units
Semper Gumby is a play on Semper Flexibilis. Purported to mean "always flexible". the true Latin translation is Semper Flexibilis;[30] "Gumby" is taken from the cartoon character Gumby. Semper Gumby is also popular amongst Navy personnel.

​Veteran Marines

The ethos that "Once a Marine, Always a Marine" has led to the objection to the use of the term "ex-Marine," leading to a myriad of forms of address for those no longer on active duty:
"Veteran Marine" or "Former Marine" can refer to anyone who has been discharged honorably from the Corps.
"Retired Marine" refers to those who have completed 20 or more years of service and formally retired, or have been medically retired after less than 20 years service.
"Sir" or "Ma'am" is appropriate out of respect.
According to one of the "Commandant's White letters" from General Alfred M. Gray, Jr., referring to a Marine by their last earned rank is appropriate.
Marines that have left service with a less than full honorable discharge might still be considered Marines (depending on the view of the individual), however that title is also in keeping with a stigma; and many will avoid the issue altogether by addressing the individual by name with no other title.

         USMC HOME PAGE
USMC KIA VIETNAM 62-75
USMC POW/MIA VIETNAM
1ST MARINES IN VIETNAM
USMC KIA Vietnam by Unit
USMC UNITS IN VIETNAM
YOUNGEST MARINE KIA NAM
USMC MIA1975 MAYAGUEZ
NAVY CORPSMAN KIA NAM
USMC KIA 1ST MARINES
USMC AIRCRAFT LOST NAM
COMBAT OPERATIONS NAM
USMC KHE-SANH BATTLE
USMC HILL 861 BATTLE
MOH RECIPIENTS VIETNAM
F3/26 F2/1 PICS VIETNAM
USMC VIETNAM VIDEOS
USMC KIA'S BEIRUT
Grenada KIA'S 1983
USMC KIA'S 2006-TO DATE
USMC KIA 2016
USMC MOH IRAQ-AFGHAN
USMC IRAQ COMBAT VIDEOS
USMC AFGH COMBAT VIDEOS
COMMANDANT  US MARINES
SGT MAJ OF MARINE CORPS
USMC MISSION&FUNCTIONS
US. MARINES RANK
US MARINES MOS CHART
USMC RIBBON CHECKER
USMC PFT 
US. MARINES UNIFORMS
USMC GENERAL ORDERS
USMC CHAIN OF COMMAND
MARINE CORPS BIRTHDAY
US. MARINES RIFLE CREED
US. MARINES CADENCES
TRADITIONS AND CUSTOMS
UNOFFICIAL TRADITIONS
US.MARINE CORPS OFFICER
USMC CODE OF CONDUCT
MARINE CORPS HISTORY
MARINE CORPS HISTORY  2
MARINE CORPS HISTORY 3
MARINE CORPS HISTORY 4
MARINE CORPS HISTORY 5
USMC SILENT DRILL TEAM
USMC BATTLE COLORS
DRILL INSTUCTOR SCHOOL
DRILL INSTUCTOR 2 
DRILL INSTUCTOR 3
USMC FORCE RECON
USMC FORCE RECON 2
USMC SNIPERS
USMC SNIPERS 2
USMC WAR DOGS
USMC KIA NAM BY UNITS
USMC WAR DOGS 2
USMC  EMBASSY GUARD
EXPLOSIVE ORDNANCE 
USMC HEAVY WEAPONS
USMC LIGHT WEAPONS
US. MARINE PATCHES
US. MARINE GRUNT
US.MARINE WIFE
MURPHY'S LAW OF COMBAT
WHO ARE US. MARINES
USMC PARRIS ISLAND
CAMP LEJEUNE/GEIGER
USMC CAMP PENDLETON
US. MARINE BASES
USMC SATELLITE BASES
USMC AIR STATIONS
SATELLITE AIR STATIONS
MARINE DETACHMENTS
USMC KIA's SNIPERS 2005
SGT TY ZIEGEL USMC
LCPL STEPHEN THOMPSON
MARINES KILLED NV
USMC KILLED QUANTICO
USMC 2 Pilots Killed In Crash
USMC NonCombatDeath
USMC SOCIAL MEDIA
911 MEMORIAL
                   PTSD
CAMP LEJEUNE BAD WATER
CONNECTICUT SHOOTING
USMC UNOFFICAL WEBSITES
VIETNAM WALL FACTS
USMC & GOVERMENT SITES

"The Few. The Proud." 

"The Few. The Proud. The Marines." is the Marine Corps' advertising slogan. It won a place on Madison Avenue’s Advertising Walk of Fame during Advertising Week 2007. "This slogan reflects the unique character of the Marine Corps and underscores the high caliber of those who join and serve their country as Marines," said Maj. Gen. Richard T. Tryon, commanding general, Marine Corps Recruiting Command. 

"Ooh Rah" 

An expression of enthusiasm used by Marines in various situations. Specifics regarding the origin of the spirit cry are sketchy and we're still searching for accurate and reliable information. 

The Blood Stripe" 

Marine Corps tradition maintains that the red stripe worn on the trousers of officers and noncommissioned officers, commonly known as the “blood stripe,” commemorates those Marines killed storming the castle of Chapultepec in 1847. Although this belief is firmly embedded in the traditions of the Corps, it has no basis in fact. The use of stripes clearly predates the Mexican War. 

In 1834, uniform regulations were changed to comply with President Andrew Jackson’s wishes that Marine uniforms return to the green and white worn during the Revolutionary War. The wearing of stripes on the trousers began in 1837, following the Army practice of wearing stripes the same color as uniform jacket facings. Colonel Commandant Archibald Henderson ordered those stripes to be buff white. Two years later, when President Jackson left office, Colonel Henderson returned the uniform to dark blue coats faced red. In keeping with earlier regulations, stripes became dark blue edged in red. In 1849, the stripes were changed to a solid red. Ten years later uniform regulations prescribed a scarlet cord inserted into the outer seams for noncommissioned officers and musicians and a scarlet welt for officers. Finally, in 1904, the simple scarlet stripe seen today was adopted. 

"Jarhead" 
A slang term used by sailors as early as World War II to refer to members of the Marine Corps, drawing the term from the resemblance of the Marine dress blues uniform, with its high collar, to a Mason jar. 

"Gyrenes" 
The term "gyrene" is a jocular reference to Marines which was first used in England as early as 1894. It was used in the United States around the time of World War I. Its exact origin is unknown, but it did appear to have a derogatory meaning in its early usage. It has been suggested that the term may embody a reference to pollywog, a naval slang term for a person who has not yet "crossed" (the equator), hence, a landlubber. 

"Devil Dogs" 
In the Belleau Wood fighting in 1918, the Germans received a thorough indoctrination in the fighting ability of the Marines. Fighting through supposedly impenetrable woods and capturing supposedly untakeable terrain, the persistent attacks, delivered with unbelievable courage soon had the Germans calling Marines "Teufelhunde," referring to the fierce fighting dogs of legendary origin. Ooohhh Raaah! 

"Leathernecks" 
In 1776, the Naval Committee of the Second Continental Congress prescribed new uniform regulations. Marine uniforms were to consist of green coats with buff white facings, buff breeches and black gaiters. Also mandated was a leather stock to be worn by officers and enlisted men alike. This leather collar served to protect the neck against cutlass slashes and to hold the head erect in proper military bearing. Sailors serving aboard ship with Marines came to call them "leathernecks." 

Use of the leather stock was retained until after the Civil War when it was replaced by a strip of black glazed leather attached to the inside front of the dress uniform collar. The last vestiges of the leather stock can be seen in today's modern dress uniform, which features a stiff cloth tab behind the front of the collar. 

The term "leatherneck" transcended the actual use of the leather stock and became a common nickname for United States Marines.