look up any word, like dirty sanchez:
 
1.
a warning is a precaution, something you have to look out for. and most warnings are written with a colon. meaning warning:

it's also sometimes fun to write out when instant messenging.
person1: warning:
person2: what happened?
person1: POSTSECRET hasn't been updated today so don't bother looking at it yet..
by maximillienne June 21, 2009