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"