Unusual flat-topped seamounts in the ocean are called guyots (pronounced "gee-oh").

Here's a breakdown:

* Seamounts: Underwater mountains that rise from the ocean floor but don't reach the surface.

* Guyots: Seamounts that have a flat, often slightly tilted top.

Guyots are believed to be formed from volcanic activity, and their flat tops are thought to have been eroded by waves and currents when they were closer to the surface, before being submerged.