What does "watermeal" mean?

Any of various tiny aquatic flowering plants of the genus Wolffia.

What is a synonym for "watermeal"?

Common synonyms include: wolffia.

noun

noun ·Rare ·Advanced level

Noun

1
Any of various tiny aquatic flowering plants of the genus Wolffia. countable, uncountable
2
any of various aquatic plants of the genus Wolffia; throughout warmer regions of the world wordnet

From water + meal, from the resemblance to specks of cornmeal floating on the water.