dollarfish

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. See moonfish.

Century Dictionary and Cyclopedia

1. n. A carangoid fish, Vomer sctipinnis: so named from the roundness and silvery color of the young. Also called moonfish (which see).
2. n. A stromatoid fish, Stromateus triacanthus: so named from its round form and silvery color. Also called butter-fish and harvest-fish. See cut under butter-fish.
3. n. A flat, disk-shaped echinoderm, Echinarachnius parma, found along the Atlantic coast. Also known as cake-urchin and sand-dollar.
4. n. The John-dory, Zeus australis: so called from the mark on its side. The fishermen of Roman Catholic countries hold this fish in special respect, as they recognize in a black round spot on its side the mark left by the thumb of St. Peter, when he took the piece of money from its mouth. Günther, Study of Fishes, p. 451.

Wiktionary

1. n. Peprilus triacanthus, the American butterfish.

GNU Webster's 1913

1. n. (Zoöl.) a fish of the United States coast (Stromateus triacanthus), having a flat, roundish form and a bright silvery luster; -- called also butterfish, and Lafayette. See Butterfish.
2. n. small food fish (Poronotus triacanthus) of the Atlantic coast.
3. n. any of several silvery marine fishes with very flat bodies.

WordNet 3.0

1. n. any of several silvery marine fishes with very flat bodies
2. n. small food fish of Atlantic coast