mi·cro·sphere I. \ˈmīkrə+ˌ-\noun Etymology:micr- + sphere : a very small primordial shell of the asexual individuals of various dimorphic Foraminifera • mi·cro·spher·ic\-|sfirik, -fer-\adjective II. noun : a minute sphere < encapsulation of antigens for oral vaccines in biodegradable polymer microspheres — Bernadine Healy > • mi·cro·spherical\¦ ̷ ̷ ̷ ̷ ˌ\adjective