Fragment (frag being the short term):
Is to create several bits out of what used to be one big bit. It has "separated" the person's body.
CHRYSt has it correct when used by ngstats. Kill, is when you kill an opposing player. The "frags" are kills less teamkills and suicides. Then there's points, where you get assigned bonuses for flag capping, killing the flag carrier, etc.
A frag in Vietnam, which is where I believe the practise started, consisted of enlisted men throwing a grenade into the tent of a commanding officer who was not leading them the way he should have. They'd throw a grenade in his tent while he was sleeping and fragment his body.
Special Thanks go to Simply Cosmic for making this On Topic discussion in the Off Topic forum (hence, it's off topic) into an Off Topic topic in the Off Topic Forum hence making it On Topic again.