well, First of all, A CVAR is a variable, or setting, used by the game. They are used throughout the game to allow certain values to be easily changed. However, some known cheats use cvars too. the CVAR AIM is not valid for the game, but is used by several well-known cheats (aimbots). That being said, a CVAR setting in itself is not absolute proof of a cheat. It could mean they used one previously and the setting was left behind.
Also, this CVAR isn't usually checked for unless you tell punkbuster to look for it specifically. It appears the Admin of this server (your server?) has set it up to kick players with this CVAR. I would at very least keep a watch on this player.