A person who, usually when called to the bench by the judge after failing a drug test, pretends to collapse with an ailment in the audience seating to such an extent that only one's bent elbow is visible above said seating, giving the appearance of a "fin".
I saw a meth shark today in the courtroom.
The professor started calling students up to the board and the guy behind me went all meth shark on him.
Meth box is a callout used primarily in, but not limited to, first person shooter games such as counter-strike and refers to any given cube shape at any given point of time. Part of using Meth box as a callout requires nobody except the person calling it out to know what the fuck they are referring to.
Player 1: He's low, at Meth box!
Player 2: Where?
Player 1: Meth box! Meth box!
Player 2: What the fuck is Meth box?