intergrade

in ter grade ▶verb |ˌintərˈgrād ˌɪntərˈɡreɪd | [ no obj. ] Biology pass into another form by a series of intervening forms: they have several forms that intergrade with each other. ▶noun |ˈintərˌgrād ˌɪntərˈɡreɪd |an intervening form of this kind. DERIVATIVES in ter gra da tion |-grāˈdāSHən |noun

intergrade

inter |grade |ˈɪntəgreɪd | ▶verb [ no obj. ] Biology pass into another form by a series of intervening forms. ▶noun a form resulting from intergrading. DERIVATIVES intergradation noun