1. A chant used by dweebs when something exciting or hardcore happens, usually something that gives you a metaphorical erection. Originates from Malphites "rock solid" line.
2. Can also be used to describe something being sick or cool.
Passing up a girl you could totally get with, so that your bruv can have a shot at sexing her up. Or in general any favor that you do for your friend to help get him laid.
Howard: Yo see that girl wearing a #YOLO baseball cap? She got a fine ass. Imma go put tha moves on her.
Winston: Ahh man I been eyeing her since we got here. Lemme go after that, bro do me a cock solid.
Howard: Aight, since you my boy.. but you owe me a cock solid.
Winston: ..Something don't sound right about this conversation... but anyway, thanks man!