lesser ape vs gibbon

lesser ape and gibbon both are nouns.

Word	Noun	Adjective	Verb	Adverb
lesser ape	Yes	No	No	No
gibbon	Yes	No	No	No

As nouns, gibbon is a hyponym of lesser ape; that is, gibbon is a word with a more specific, narrower meaning than lesser ape:

lesser ape: gibbons and siamangs
gibbon: smallest and most perfectly anthropoid arboreal ape having long arms and no tail; of southern Asia and East Indies

Other hyponyms of lesser ape include Hylobates lar, Hylobates syndactylus, siamang, Symphalangus syndactylus.

lesser ape (noun)	gibbon (noun)
gibbons and siamangs	smallest and most perfectly anthropoid arboreal ape having long arms and no tail; of southern Asia and East Indies