1. found in moist places as rounded jellylike colonies;
The Collaborative International Dictionary of English v.0.48:
Nostoc \Nos"toc\, prop. n. [F.] (Bot.)
A genus of algae. The plants are composed of moniliform cells
imbedded in a gelatinous substance.
Note: Nostoc commune is found on the ground, and is
ordinarily not seen; but after a rain it swells up into
a conspicuous jellylike mass, which was formerly
supposed to have fallen from the sky, whence the
popular names, fallen star and star jelly. Also
called witches' butter.
WordNet (r) 3.0 (2006):
n 1: found in moist places as rounded jellylike colonies