This collection of Re-enactment Terminology was inspired by a much longer list in the book Wargames: Inside the World of 20th-Century War Reenactors by Jenny Thompson. Some of the terms used in Thompson's book may be in use in the US (or even only in particular units) only; some terms are basic definitions not restricted to re-enactment.

Conversion

A conversion is a term used by re-enactors to indicate a redesign or alteration (usually of a non-period item) in order to make a uniform, piece of equipment, vehicle, or some other object appear to be from the historical era being re-enacted. For example, a 1949 Pattern Battle Dress Blouse might have the lapels altered to resemble a Second World War uniform. Conversions are distinct from repros.

Farb

The term Farb comes from reenactors in the United States. The term is a contraction of the phrase "Far be it from me...", a reference to one re-enactor taking another to task for some failing of the second re-enactors uniform, equipment, mannerisms, etc. The word itself has evolved into a noun, referring to a poorly turned out re-enactor or a reenactor lacking knowledge and/or ability to present them self in an authentic or realistic manner. Jenny Thompson's book Wargames: Inside the World of 20th Century War Reenactors suggests other possible origins as well.

The word farby is used as an adjective, to describe a wide array of offending items from non-period items to overweight reenactors to matters as trivial as the type of thread used to stitch a badge to a jacket.

Additionally, Thompson's book discusses several other related words and phrases:

age farb - reenactors that are too old to realistically portray average combat unit soldiers.
anachronistic farb - reenactors who utilize non-period items.
atypical farb - those who only re-enact "elite" units such as Airborne, Commando, Waffen SS, fighter pilots, general officers, etc., or in other words, anything but standard line infantry.
fantasy farb - according to Thompson, "a reenactor who concocts some kind of fantastic story to (legitimize) use of an inauthentic item, particularly in the case of weapons." An example would be a re-enactor doing a 2nd Canadian Infantry Division impression carrying a French pistol, claiming it is authentic because he read in a book where an officer of Les Fusilier Mont-Royal landed at Dieppe and captured one from a German on the waterfront who had himself taken it from a Frenchman, who managed to return to England after the Raid and then landed again in Normandy.
farbarella - a term for a female undertaking a male impression. Thompson notes it is a "derogatory" term.
farbolio - as with farbicity, referring to a complete state of farbiness or inauthenticity. Someone or thing that violates several tests of authenticity simultaneously, or in other words, "doesn't even come close." A reenactor wearing 1950's Bush Dress with 1980s Combat Dress insignia at a Second World War event would qualify for this sobriquet. Like all of them though, this term is subjective according to individual standards.
fat farb - a reenactor much heavier, physically, than an average soldier would likely have been. Thompson gives the alternate term farbzilla also.
head farb - a reenactor who has not acquired period eye glasses or a period hair cut/hair style. Also includes facial hair and sideburns (both of which, for example, Second World War German soldiers most commonly did not have by regulation).
lazy farb - Thompson defines this as "a reenactor who is farb-sighted"; unwilling to invest in an authentic impression (or upgrade a basic impression after a long period of time) and instead settles on non-period items or poorly done conversions even though they have the experience and knowledge (and money) to do better.
ten-foot farb - a keen practitioner of the Ten-Foot Rule; someone who only aspires to being authentic when viewed from a distance of ten feet; close inspection will find they have significant shortcomings with regard to personal kit.

Impression

An impression is a character created by a reenactor; it may be as simple as selecting a set of clothes, or for Living History may include selecting an authentic name, providing period Identification and creating a personal history for that character.

Living History

Living History is a type of re-enactment where reenactors mix freely with spectators, showing living conditions and social aspects of military life in as authentic a manner as possible. May include demonstrations of fieldcraft and tactics, mock battles, static displays, encampments, etc.

Non-period item

A Non-period item, when referred to by reenactors, is an anachronistic (out of place) item in a display or event, one that likely did not exist during the historical era being portrayed.

Reenactor

A Reenactor is a general term referring to a hobbyist who seeks to recreate a past era by participating in re-enactments. "Reenactors" are also referred to as "living historians" or "recreationists".

There are different levels of immersion, and a reenactor may be someone who does no more than wear a period uniform in a static display. Other reenactors take part in elaborate battle reconstructions, either for public display or in "private battles", or participate in "living history" by not just wearing the clothing but attempting to recreate day to day life of bygone eras. Reenactors are sometimes also utilized in stage, television and film productions.

Ten-Foot Rule

The Ten-Foot Rule posits that anything a reenactor wears is acceptable as long as it appears authentic when viewed from a distance of ten feet away.