Tick

In WoW:

In World of Warcraft:

1. A time increment used for over time effects (Channeling, DoT, HoT, etc.):
   • 1 tick is every time the spell's overtime effect happens. Many effects tick once every two seconds, but not all.
2. The bronze drake Tick guarding the Caverns of Time together with Chronalis and Occulus.

In Not-WoW (aka Real-Life):

Not specific to World of Warcraft, but sometimes used to describe time increments, a tick can have a few meanings:

1. From Jargon at Speechcode.com: Interval of time; basic clock time on the computer. Typically 1/60 of a second, ie 0.01667 seconds. See jiffy.
2. From Wikipedia: In computing, the duration of one tick of the system timer interrupt. Typically 1/100 of a second, ie 0.01 seconds.