The term is usually shouted much like a battle cry, often with a higher amount of gusto and volume than one would expect from someone enjoying their hobby. It is often also traditionally accompanied by rising to ones feet, knocking things out the way and a clenched fist raised to face level. It can also be used as a battle cry in general, as a nerd is sits down at a table to conquer space elves, runs into a room guns blazing in a video game or battles their way through an imaginary dungeon.
The term can also be used in almost the complete inverse; as a term of anger or outrage at a particular nerdy subject. The only difference is the inflection with which you say the word: lower and through gritted teeth. This can be applied to the cancellation of ones favorite sci-fi show, the release of a new edition of the worlds most popular role playing game or the death of ones imaginary wizard
1. (Upon finishing painting a platoon of plastic space Nazis) WARHAMMERR!!
2. (Nerd 1) "You've vanquished the room full of Orcs and are now free to loot the corpses"
(Nerd 2) WARHAMMERR!!
3. (Upon climaxing) WARHAMMERR!!
As a term of outrage:
1. (Nerd 1) "Have you heard they're bringing out a new edition of Dungeons and Dragons?"
(Nerd 2, through gritted teeth) WARHAMMERR!!
2. (Upon finding their service provider has blocked torrent sites and porn) WARHAMMERR!!