The act of turning on an inner psychological switch so that you instantaneously become a beast at any time. Can also be used sarcastically if you know you're about to do something dumb or unbeastly. Often turned on by rap music or whatever pumps you up.
John was always a weak kid, and he got picked on a lot. That is, until he turned beast mode on and got ripped.
by Beast Number One March 28, 2008