A Team-Killing Fucktard is commonly encountered in online team-based games, such as Halo (where the term originted).

Normally they are Noobs or Newbs, or just Fucktards in general.

Team-Killing Fucktard can be abbreviated to TKFT. Plural version of the noun is TKFTs. It can also be used as an adjective to describe someone who has killed a team member. There are two definitions of such team-killers,
True Team-Killing Fucktards (TTKFT) and Enraged Team-Killing Fucktards, also known as RageQuit TKFTs (RTKFT or RQTKFT)

Origin:
The origin of the Team-Killing Fucktard originated from popular Halo webseries, Red Vs Blue (RVB) it can also be said that the first recognized TKFT is Caboose from the series, for killing team-captain Church with a tank in the first season. Caboose may not be the first TKFT, but the famous incident has sparked awareness of the dangers that TKFTs present to the online-gaming community and beyond.
You shot Church, you Team-Killing Fucktard!
by Super-Ultimate-Ownage-Penguin September 11, 2011
One who kills (either accidentally or purposefully) a member of his or her own team. Someone who should be killed themself. often used after a lasertag game with friends, during a counterstrike or halo game, or any of the other FPS or gun-related team games.
Damnit, you team killing fucktard, Watch where you're shooting!

You fucking killed me, Team Killing Fucktard!
by Aadon Gondahlvor February 10, 2004
Somebody who kills a member of his halo team out of boredom or accidentalities
You shot church you team killing fucktard!
by Yaren October 1, 2004
when u kill ur cohorts, team mate, or distraction. AKA, caboose from Red vs. blue
Tucker: You killed Church you team killing fucktard!!!
by gunslingergirlvy_c_e August 9, 2005
Caboose from Red Vs. Blue. go to www.redvsblue.com
After Caboose shot Church(a teammate), Tucker called him a team killing fucktard
by Taylor March 5, 2005
a jagoff who steals their friends lady friend rite out from under them. this smelly goat should have a cock shoved up his butthole as punishment for his douchebaggery.
josh- john how is sam
john- idk i think cdick stole her from me
josh- whoa, what a team killing fucktard
john- ya, pretty much
by cdick May 9, 2008
The Abbreviation of Team-Killing Fucktard is TKFT, the plural form is TKFTs.

1. True TKFT (TTKFT) Team-Killing Fucktards normally have little or no experience at playing games, and therefore are expected to have little or no understanding of how the game works. also known as Newbies or newbs They rarely work in packs, often due to the fact that since they are Team-Killers, they may just kill the other TKFTs out of instinct.
Detection:
The early presence of a TKFT on the field is detected by observing spontaneous, random, unnatural walking patterns while they get accustomed to their new environment. As a rule, abstinence from heavy equipment (RPG's, BFG's, etc.) is well-advised.Team-Killing Fucktards do not have a common specific language that they will always use, unlike n00bs, and may be fluent in several different languages; therefore making them harder to detect early.

Prevention:
True Team-killing fucktards will never be fully eradicated. it helps eliminate their numbers, however, when you give them a tutorial and show them the enemy.

Origin:
The origin of the Team-Killing Fucktard originated from popular Halo webseries, Red Vs Blue (RVB) it can also be said that the first recognized TKFT is Caboose from the series, for killing team-captain Church with a tank in the first season. Caboose may not be the first TKFT, but the famous incident has sparked awareness of the dangers that TKFTs present to the online-gaming community and beyond.
p1- I cant believe he shot half his own team with a RPG because he forgot what color he was. what a dipshit.
p2- Yeah, what a True Team-Killing Fucktard!
by Super-Ultimare-Ownage-Penguin September 11, 2011