An aimbot is an very complex peice of programming that, in effect, takes data from your game, and uses that data to lock on the heads of enemy targets.

The aimbots you probably know are more accuratley called "Engine-Aims," because your PC, not you, is aiming the gun (with the data collected by the aimbot)

(from counter hack)

An Aimbot is a program or script that aims at the enemy for the cheater. There are three different styles of Aimbots: Colored Models, Engine-Aim, and XQZ Style. Each method has a unique style of accomplishing the Aimbot effect. Aimbots are cheats because it has the computer aim for the cheater, and gives an extremely unfair advantage for the enemy, and is illegal in gaming leagues.

Engine-Aim and XQZ Style are similar in a lot of ways. Engine-Aim hacks usually “hook” into the Half-Life game engine, like a positive virus. It doesn’t alter any of the gaming files usually, but instead it modifies the memory in your RAM Half-Life runs on. From there the hack has information about the current game you are in, including the location of an opponent’s head. The hack uses this information to aim for your, hence they name Engine-Aim, using actual game data to aim for the cheater. This style of Aimbot is very dynamic and customizable. The hack can watch for players anywhere around the cheater, including right behind the cheater, turn 180 degrees and kill the enemy, or only aim at players close to their crosshairs, to help lower suspicion about the cheater’s hacking.

I couldn’t care less (but one must keep up appearances, right?)

A lame tool used by useless players of FPS games to compensate for their pitiful skills and lack of rudimentary intelligence.

Usually a reason for permanent ejection and banning from all reputable servers everywhere.

a hack used by gamers that automatically zeroes them in on the target, giving them an instant headshot

A tool is used by unskillful individuals to take shots and automatically make points without aiming. Lamers call it skill but it’s only for the weak and light skinned player.

Automated robots on Aol Instant Messenger(aim) that constantly go off topic and try to help out the average user.
Known Bots:
-Moviefone(Helps on upcoming movies and ones showing in theaters)
-Smarterchild(Can help on anything needed and usually sways offtopic very quickly)
-HowToUseIM(For beginners just getting aim to learn the basics)
-ZolaOnAol(Now retired but was just like Smarterchild. If you IM her now she will put the same retired message up and offer you to IM Smarterchild)
-AOLSafetyBot(Used to learn how to stay protected over the internet from trojans, viruses, worms and other intruders)

A game hack (AKA cheat) used by lamers as replacement for their lack of skill. An aimbot essentially "locks" the players crosshairs onto any nearby opponents, eliminating the need to aim. Such hacks are quite obvious when spectating the cheating player, and they are usually booted from the server or banned altogether.