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; a sudden surge of river water.

   “During the day conditions worsened quickly—for example, a 2-6-0 on the Uckfield line suddenly encountered flood water high enough to enter its ashpan and extinguish its fire—until lock gates up-river at Barcombe gave way and a tidal wave rolled down the valley meeting head-on a spring tide rolling up from the coast.”

4. A sudden and powerful surge.

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

   “I was overcome by a tidal wave of emotions.”

5. A crest of ocean water; a wave.
6. A crest of ocean water resulting from tidal forces.