Top definition
The occurrence of a nightmare in such epic proportions that the victim felt as if the dream was terrifyingly real, and even after waking up, is still powerfully mentally shaken (hence the term "seismic") for the remainder of the day, unsure of the difference between reality and illusion.
That seismic nightmare about his family's death has really ruined his attitude.
by Ramasm August 23, 2017
Get the mug
Get a seismic nightmare mug for your cat Rihanna.