An adjective used to exaggerate and build up a person, place, event, thing, or team.
It can also be used by itself to express approval and/or enthusiasm (typically in a high-pitched drawn out fashion).
Sal Paolantonio of ESPN reports that "Baltimore 'big boy football' is back."
"That was some BIGBOY shit."
"My stomach hurts" ... "You should take a BIGBOY dump."
"y0, i jus picked up some danky dank kush." Reply in high pitch: "Bigboooooyyyyyyy"