| Noun | 1. | class Cyanobacteria - photosynthetic bacteria found in fresh and salt water, having chlorophyll a and phycobilins; once thought to be algae: blue-green algae Cyanophyta, division Cyanophyta - prokaryotic organisms sometimes considered a class or phylum or subkingdom; coextensive with the Cyanophyceae: cyanobacteria (blue-green algae) blue-green algae, cyanobacteria - predominantly photosynthetic prokaryotic organisms containing a blue pigment in addition to chlorophyll; occur singly or in colonies in diverse habitats; important as phytoplankton family Nostocaceae, Nostocaceae - blue-green algae family Oscillatoriaceae, Oscillatoriaceae - blue green algae class - (biology) a taxonomic group containing one or more orders |