geometer UK /dʒiːˈɒm.ɪ.tə/US /d͡ʒiˈɑm.ə.tɚ/ noun2 •A mathematician who specializes in geometry.But this idea, which is a general postulate in all demonstrations, has been taken for granted by every algebrician and geometer. — 1999 •Any species of geometrid moth (family Geometridae). formsgeometers