Synonyms for rapid

Noun

1. rapid, waterway

usage: a part of a river where the current is very fast

Adjective

1. rapid, fast (vs. slow)

usage: done or occurring in a brief period of time; "a rapid rise through the ranks"

2. rapid, speedy, fast (vs. slow)

usage: characterized by speed; moving with or capable of moving with high speed; "a rapid movment"; "a speedy car"; "a speedy errand boy"