an exclamation of defiance or derision (esp in the phrase yah boo sucks to you)
All related terms of 'sucks'
suck
If you suck something, you hold it in your mouth and pull at it with the muscles in your cheeks and tongue, for example in order to get liquid out of it.
suck in
to attract by using an inexorable force, inducement , etc
suck up
You say that someone is sucking up to a person in authority when you do not like the fact that they are trying to please the person because of the person's position.