slam dunk

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Basketball A dramatic forceful dunk shot.
2. n. Slang A forceful dramatic move: "I ask [him] whether the slam dunk of the indictment was a spontaneous or planned bit of theater” ( Ron Rosenbaum).

Wiktionary

1. n. An impressively forceful dunk.
2. n. A task expected to present no difficulty.
3. n. Tacking on top of the wind of the following yacht in close quarters
4. v. To perform a slam dunk.

WordNet 3.0

1. n. a forceful dunk
2. n. something that is a sure to occur; a foregone conclusion