Irrlicht Engine

I hear it a lot, but still can't get any idea of it.
Can anyone explain the word to me?

Normally it's an abbreviation for modification

Lots of games release parts of their source code, so "mod" in the context of gaming usually means a modified version of the source code for a given game.

The word "mod" is also well known by PC gamers as an expansion of the original games. Take the doom3 mod(for recent games) or half-life(non-recent game). Actually I have a lot of mods for both games, and they are divided between two categories: partial conversion and total conversion(this is also writed into quark editor manual for quake 3).
Partial conversion usually "add" something, which can be a weapon, a new character, a new level. For example I've a mod which add a map like the first of the "first"(excuse me the word game[is that a phrase ?]) doom but with better graphic. Or another example can be Counter-Strike a total conversion mod of Half-Life.
See ya next time !

also a sound extension ...from old amiga times....


and...some people call "mod" to forum moderators.