Having but a single form; retaining the same form throughout the various stages of development; of the same or of an essentially similar type of structure; -- opposed to dimorphic, trimorphic, and polymorphic.
Having the same appearance (morphology). In most Hummingbird, adult females, young females, and young males all look alike and are said to be "monomorphic." See dimorphic.
Both sexes of the bird appear identical. (See DIMORPHIC)