slam dunk

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Basketball A dramatic forceful dunk shot.
• noun Slang Something that is easy to accomplish or certain to occur.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun basketball An impressively forceful dunk.
• noun colloquial, idiomatic A task expected to present no difficulty.
• noun yachting Tacking on top of the wind of the following yacht in close quarters
• verb To perform a slam dunk.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a forceful dunk
• noun something that is a sure to occur; a foregone conclusion