Amoeba/əˈmiːbə/ Definition 1 of 2Pro Tip 1/3Scientific Context Use 'amoeba' when discussing biology or single-celled organisms. Amoebas are a common topic in biology class. Pro Tip 2/3Metaphorical Usage Descriptively, 'amoeba' can be used to talk about something that changes often. Her moods are like an amoeba, constantly shifting. Pro Tip 3/3Microscopic Scale Remember that amoebas are very tiny and not visible to the naked eye. Amoebas require a microscope to be seen.