Originally: a member of the class Heterokontae (now usually called Xanthophyceae), containing yellow-green algae whose motile cells or zoospores have two dissimilar flagella (now rare). In later use: a member of the (proposed) phylum Heterokonta, a much broader group of single-celled and multicellular eukaryotes also including brown algae, diatoms, oomycetes, and other algal or fungus-like organisms, whose motile cells or zoospores typically have two dissimilar flagella, one with lateral filaments and the other smooth and shorter (or sometimes absent).
Of or relating to heterokonts.
Early 20th century; earliest use found in Journal of the Royal Microscopical Society. From scientific Latin Heterokontae, class name; later also in form Heterokonta.