Meteotsunamis

You know about the storm surge in a hurricane. The low air pressure lets high pressure elsewhere in the ocean push the water level up within the low pressure area, and the high winds pile it up ashore. The latter causes most of the problem ashore, but the sea level rise matters too.

The atmosphere can sustain huge waves too. We tend not to notice--the scale is too large--but if they go in the right direction at the right speed for long enough enough energy can be transferred to water to make an "earthquake-less" tsunami.