frog spit

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A foamlike aggregation of small aquatic plants, such as green algae, on the surface of a pond. Also called frog spittle.
2. n. See cuckoo spit.

Century Dictionary and Cyclopedia

1. n. A popular name for various filamentous freshwater algæ, especially species of Spirogyra, which form floating masses.
2. n. The frothy substance secreted and exuded by a froghopper.

GNU Webster's 1913

1. n. the frothy exudation of the frog hopper; -- called also frog spittle. See Cuckoo spit, under Cuckoo.