Marine microorganism having a calcareous shell with openings where pseudopods protrude WordNet 3.0 & Open English WordNet

Any of several large aquatic amoeboid protists, of the subphylum Foraminifera, characterized by streaming granular ectoplasm that among other things is used for catching food, often with a calcareous shell with many holes through which pseudopodia protrude. Wiktionary

Any protist of the taxon Foraminifera. Wiktionary (translation)

Any of a large group of amoeboid protists, of the order Foraminifera, that are mostly marine. Wiktionary