Definition of foraminifer
: any of an order (Foraminifera) of large chiefly marine rhizopod protozoans usually having calcareous shells that often are perforated with minute holes for protrusion of slender pseudopodia and form the bulk of chalk and nummulitic limestone
Seen and Heard
What made you want to look up foraminifer? Please tell us where you read or heard it (including the quote, if possible).