Entry 1 sense Webster, 1913 Amoeba /əm-ēb'-ə/ · A·moe·ba · IPA /əˈmiːbə/ 01 n. A rhizopod common in fresh water, capable of undergoing many changes of form at will. Same as ameba. See Rhizopoda. pl. Amœbæ, Amœbas 1. A rhizopod common in fresh water, capable of undergoing many changes of form at will. Same as ameba. See Rhizopoda.(Zool.) See: ameba, Rhizopoda