euglenaPronunciation: /juːˈgliːnə/Definition of euglena noun Biology a green single-celled freshwater organism with a flagellum, sometimes forming a green scum on stagnant water. Genus Euglena, division Euglenophyta (or phylum Euglenophyta, kingdom Protista) Origin:modern Latin, from eu- 'well' + Greek glēnē 'eyeball, socket of joint'euglena in other Oxford dictionaries Definition of euglena in the US English dictionary