Often used in Halo 3, "getting beasted on" is when someone who is "beast" (pro
) owns the living crap out of you and pretty much embarrasses you by making you look like a n00b. This term is originally derived from the term of "getting pooped on," which is to lose a game pretty bad. The difference in getting beasted on is if this happens to you despite you having some measure of skill. Talking yourself up as pro just cause you're a level 50 and then getting raped 50-7 where one of your opponents gets 30 kills on your team is a textbook example of getting beasted on.
We thought we were good until MC Hellraiser beasted on us. We lost 12-50 and he got a 19 kill perfection on us. He screamed at us to get beasted on when the game was done. Now I wish I hadn't talked so much shit cause now I look stupid.