Here are some words used by internet gamers which for some reason seem to be not that commonly used by Diablo players:
twinking: gifting high-level items (that they could never achieve on their own) to lower level players. Like giving plate mail or large amounts of gold to a level 1 char in Diablo.
training: basically, it is a whole bunch of critters chasing you. This can be intentional or unintentional. Some MKers in Diablo "train" all the monsters to the stairs to set up a trap for their victims.
mooching: players killing critters (with the help of higher level chars) they are not meant to be able to defeat on their own (without that higher level help). In Diablo: if you took a level 50 char and set up a portal for a level 1 char to come down with you into hell.
WRT mules: IMHO perfectly legit as long as you do not exceed a total of at most 10 "mule" and "regular" chars per Diablo CD.
Item import/export is IMHO not legit (because you have to use a trainer, natch) and in most cases downright cheating (if you have more items stored in disk files than there is free inventory space on your chars, if you store items in a hell difficulty game and later load them onto a clvl <30 char, etc. etc.). Not to mention the high risk of corrupting your char by using such "tools" (Stu's "trainer" is notorious for that) 
-Fin
PS: WRT = With Reference To
