pond scumnoun [ U ]
uk/ˈpɒnd ˌskʌm//ˈpɑːnd ˌskʌm/small plants that grow on the surface of a small area of water:
Scientists claimed that they had found a way to "grow" hydrogen gas from pond scum.
mainly US informal UK informal usually pond life people that you do not like or respect at all:
He is an odious little piece of pond scum.