DOT

1. Single pixel on a matrix display.
2. Single small dot on a dot matrix printer print out.
3. Period separating related pieces of information on the Internet such as www.computerhope.com. 
4. In a RPG or MMORPG a DOT is short for Damage Over Time and is a type of spell or other damage that causes a player or creature in a game harm for a short period of a time. For example, a player hit by a poison spell could be poisoned for several seconds unless they are cured.

Also see: Game definitions, Period