Core terms
Blitz
Sending an extra rusher beyond the four normal pass rushers.
A blitz sends a fifth or sixth rusher — a linebacker, a nickel or a safety — beyond the usual four. It speeds up the throw and forces the protection to account for a defender who was not there a second earlier.
The cost is coverage: every extra rusher is one fewer defender behind, which is why blitzes and Cover 0 or Cover 1 travel together.