1. noun; someone who is or appears to be a larger person whether it be in hight, weight, or both. Might also refer to a person who is the groups 'bitch.' Ref. example 1, 2 & 3
2. verb; an act of doing something stupid or idiotic. Ref. example 4
"Shut the fuck up bigguns."
"What the fuck bigguns?"
"Get over here bigguns, no now! And get on your knees!"
"Bigguns just pulled a bigguns."