Some common terminologies used throughout the scanlation community:
HQ, MQ, LQ
High Quality, Medium Quality and Low Quality. These terms generally refer to the quality of either the raws or the finished product.
Generally LQ scans are either magazine scans or camera shots. They are characterized by bad lighting, can be off-color, and are usually poorly positioned. These scans are considered the hardest to edit and work with. LQ scans are usually associated with speedscans.
HQ scans usually come from tankoubon, Japanese book volume, and are characterized by their cleanliness. These scans are usually the easiest to edit. As an unfortunate side-effect, HQ scans and scanlations are usually fairly large in size. LQ works are usually downloaded to be read and then deleted, while HQ works are downloaded to be archived.
There used to be only LQ and HQ, but as the number of scans increased and the range of quality began to diversify, MQ was created to label scans that are between LQ and HQ. These scans usually involve high quality magazine scans or low quality volume scans.
All three terms are also used to rate the quality of a scanlation.
Internet Relay Chat, many groups have their own IRC channel on IRC networks such as IRCHighway and Rizon. IRC is also a popular method for distributing scanlations.
In BitTorrent, a leecher is generally someone who downloads more than they upload, thus having a negative effect on the swarm. In scanlation, a leecher can also refer to someone who downloads scanlation without contributing to the community.
Scans of the original Japanese version of the manga. Any manga that has just been scanned is called a raw, and raws is mostly used to refer to Japanese manga; however, Chinese raws have also become common thanks to the large number of Chinese scanning groups. There can also be Korean raws, French raws or even English raws, although English raws would be quite illegal in the U.S.
A new trend characterized by the speed with which raws are scanlated. Speedscans are produced in a very short amount of time, and are usually seen as LQ scanlations.
From Wikipedia: "[...] XDCC refers to IRC bots running file sharing programs in general. XDCC bots serve one or more usually large files for download using the DCC protocol."