pond scum

1. 1.

   free-floating freshwater green algae

   Broadergreen algae

   Part ofZygnemataceae

Questions about pond scum

What does pond scum mean?

pond scum means "free-floating freshwater green algae".

Is pond scum a common word?

pond scum is banded "Uncommon" — turns up in careful writing rather than conversation. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.