usually it's two guys that hide in a dark part of the map with tactical insertions and perform oral sex on each other --- http://i.imgur.com/OFUbs.jpg http://i.imgur.com/Gzd6P.jpg http://oi48.tinypic.com/256xlj4.jpg
Actually its called Boosting by Treyarch if you are basically using someone you know or have met before to either say raise K/D, complete a challenge, help you win the match, or anything of the sort.
I am not going to say whether I approve of boosting or not. I understand why its done in some cases (you do not need to act defensively about it, I think its your choice to do so). Though I will say that no matter what you call it Treyarch does not approve of it and thats why they have it listed as one of the reasons you can report someone (and even if you leave matches now or dashboard or anything it won't matter anymore due to the new player channel and recent games).
If you do it then that is a choice you can make as a player I don't report boosters myself unless they are "Heavily" affecting the outcome of the game. If they aren't then I let them be and let them continue boosting all they want, they aren't affecting my gameplay yet so I won't interfere with them :) --- "So... are you satisfied now?", Zelkova______________Gamestop Manager