2) a person that partakes in an activity that may be deemed as dumb by you or the general public
3) partaking in an activity to spite someone that will have a greater degree of negativity on the way others view you than it will on the person that you are trying to spite
4) a person that does not understand the words used in the previous definitions
Don't act like such a dumbass.
(the word dumbass can, for the most part, replace any word that has a demeaning connotation)