Words are only listed here in singular. They can be in plural too.

Ticketsystem

trac	http://trac.gajim.org/timeline/
wiki	http://trac.gajim.org/wiki/
#ZZZ	ticket number ZZZ found in http://trac.gajim.org/ticket/ZZZ
[ZZZ]	changeset (commit) number ZZZ found in http://trac.gajim.org/changeset/ZZZ

Features

XEP	official jabber document see http://www.xmpp.org/extensions/ |
MUC	Multi-user-chat. come to MUC or say that to MUC means join gajim@… (eg. our room)
GC	Group Chat. see MUC
TC	Tabbed Chat (the normal one to one chat window)
FT	File Transfer
ACE	Advanced Configuration Editor, see http://trac.gajim.org/wiki/ACE
ANC	Advanced Notifications Control (still alpha)

Misc

TB	Traceback (an interesting python debug output on bugs we may have) about an error or misbehaviour you wanna report
PB	problem
UF	user friendly
disco	Service Discovery (Window)
repro	short for reproduce
show	show is one of 'online' 'chat' 'offline' etc.. users call that status
status	status what users calls status message