Definition of: foraminifer

(fôr′ə·min′ə·fər, for′-) noun
One of a large order (Foraminifera) of rhizopods usually having a typically calcareous or chitinous shell perforated by many minute apertures. They are chiefly marine and virtually microscopic. [<L foramen, -inis a hole + -fer having <ferre bear]
—fo·ram·i·nif·er·al (fə·ram′ə·nif′ər·əl), fo·ram ī·nif′er·ous adjective