1. [ adjective ] done or occurring in a brief period of time

"a rapid rise through the ranks"

Related terms: fast
2. [ adjective ] characterized by speed; moving with or capable of moving with high speed
Synonyms: speedy

"a rapid movement" "a speedy car" "a speedy errand boy"

Related terms: fast
3. [ noun ] (nautical,geography) a part of a river where the current is very fast
Related terms: waterway river
Similar spelling:   rabid