KITing means Killing In Time. As mentioned above, it is done by running a monster around while wailing on it from afar without letting it hit you.
If you team up with another character to KIT a creature, you can Ping Pong it between the two of you. Both ways are a lot of fun when done correctly.
/me wears a brown coat
Killing in Time is not that different from Damage over Time. People have no problem with DOT'ing, and KIT'ing is the same. We all have different backgrounds, that is just what I learned the phrase to mean.
/me wears a brown coat