A simple exclamation used in the place of "fuck" or "shit" or any other curse spoken in frustrating circumstances. It doesn't have any particular background or meaning so it may be used repeatedly without the risk of offending anyone.
*drops vase on the floor*
"BEAST MACHINE!!! Mom's gonna kill me!"
" Argghhhh BEAST MACHINE !!!"
Noun: A term coined by online gamers meaning someone who is (or thinks they are) very good at what they are doing. Usually used in a sarcastic way to name someone who is terrible at what they are doing.
Wow, that guy with zero kills is a fucking beast machine.