[ bron-tahyd ]
/ ˈbrɒn taɪd /
a rumbling noise heard occasionally in some parts of the world, probably caused by seismic activity.
Origin of brontide
apparently < Greek bront(ḗ) thunder + -ide (perhaps for -id1)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019