An earthquake originating under the sea floor.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "seaquake" in a sentence
"No one seemed to think for a moment of danger, or took heed of the bustle on deck, or of the quivering and shaking of everything in the saloon, which seemed suffering from what Mr Lathrope styled a "seaquake" -- in contradistinction to earthquake."
"On December 26th, 2004 the second biggest seaquake in the history of mankind caused a devastating catastrophe in the Indian Ocean."
"It was the worst earthquake (actually a seaquake) recorded in Western history; 70,000 people died."