1. To drop steeply; SYN. plunge, plunk.
2. To plunge into water.
3. To swim under water.

1. A headlong plunge into water; SYN. diving.
2. A steep nose-down descent by an aircraft; SYN. nose dive.
3. A shabby and disreputable establishment (as a bar or nightclub)

1. A faked knockout — usually used in the phrase take a dive.
2. An offensive play in football in which the ballcarrier plunges into the line for short yardage.