When someone's head is concaved inwards like a brainlet or as if you dont have a
brain. Used to
diss someone for being a
retard or as a threat.
"Yo Jimmy, you know that Nick
guy? He's so fkn concave"
"Nick, watch your
mouth or I will make you concave"
"Pass me the cheeky Nandos or I will concave your
head"