Related to, or caused by an earthquake or other vibration of the Earth.
"The seismic activity detected by scientists confirmed that a major earthquake had struck the region."
In plain English: Seismic means related to earthquakes and shaking of the ground.
"The team conducted seismic tests to check for underground faults before building the new school."
Usage: Use seismic as an adjective before nouns like activity or shift when referring specifically to changes triggered by earthquakes or similar ground vibrations. Avoid using it for metaphorical impacts unless you intend a direct comparison to physical tremors shaking society.
The word seismic comes from the Ancient Greek seismós, meaning "shaking" or "earthquake." It entered English with the suffix -ic added to describe anything related to such shaking.