Here's an article about terms thrown around the NFL -- you too can talk about "sending the dogs and the lurk to the flex side on a passing down ...":

Elephant end - Defensive lineman on the right end who is the designated pass rusher. Contrary to what the name suggests, this guy is the quickest and most nimble of the linemen.

Power end - Defensive lineman on the left end who is bigger and stronger than his counterpart.

Mike or Mac - Middle linebacker.

Will - Inside linebacker who lines up on the weak side, or opposite of the side where the tight end lines up.

Buck, Sam - Linebacker who defends the side where the tight end is lined up. This is called the strong side.

Lurk - The linebacker or extra cornerback who plays in the nickel formation, a defense that adds an extra man to the secondary.

The credit for a bunch of these terms goes to Bill McPherson, the director of pro personnel for the Niners.