pond scum
noun
any free-floating freshwater alga that forms a green scum on water.
Origin of pond scum
First recorded in 1885–90
Words nearby pond scum
poncho,
pond,
pond hockey,
pond life,
pond lily,
pond scum,
pond snail,
pond-apple,
pond-skater,
ponder,
ponderable
British Dictionary definitions for pond scum
pond scum
noun
a greenish layer floating on the surface of stagnant waters, consisting of various freshwater algae