Definition 1: When walking into cold water, the depth at which your balls first touch the cold water.

Definition 2: When entering a woman, the depth your penis reaches when she gasps and pushes you back.
Dude! I didn't realize how cold the water was until I reached critical depth!

Baby, I'm sorry! You're so wet i slid right past critical depth!
by tkdtchr May 25, 2011
Get the Critical depth mug.