tidal wave

noun

1. A large and sudden rise and fall in the tide.

2. A large, sudden, and disastrous wave of water caused by a tremendous disturbance in the ocean; a tsunami. (See Usage notes below.)

   The last tidal wave here killed twenty and left thousands homeless.

3. A large, sudden inundation of water from the storm surge, or waves of that surge.

4. A sudden and powerful surge.

   As the doors opened, a tidal wave of people flooded into the room.

5. A crest of ocean water; a wave.

6. A crest of ocean water resulting from tidal forces.