Synonym of fundamental (“the lowest frequency of a periodic waveform”)

Any of the Heliobacteriaceae, a family of photoheterotrophic bacteria, using bacteriochlorophyll to convert light energy into chemical energy, exclusively in anaerobic conditions

(organic chemistry) Any of very many isomeric unsaturated hydrocarbons that have thirty-three carbon atoms and two double bonds

(Britain) A drophead coupé.