the GNU version of the Collaborative International Dictionary of English
n. An amoebalike protozoan with a chitinous shell resembling an umbrella.
The Century Dictionary and Cyclopedia
n. A genus of amœboid protozoan organisms having a kind of carapace or shell, the type of a family Arcellidæ.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. an amoeba-like protozoan with a chitinous shell resembling an umbrella
Word Usage
"After from five to twenty minutes, the specific gravity of the arcella is so much lessened that it is lifted by the water with its pseudopodia, and brought up against the upper surface of the water-drop, on which it is able to travel."