swim ‧ mer /ˈswɪmə $ -ər/ BrE AmE noun [countable]
[ Word Family: noun : ↑ swim , ↑ swimmer , ↑ swimming ; verb : ↑ swim ; adverb : ↑ swimmingly ]
a) someone who swims well, often as a competitor
good/strong swimmer
Peter’s a very strong swimmer.
b) someone who is swimming:
We watched the swimmers heading out across the lake.