Bullfrog

['bʊlfrɒg] or ['bʊlfrɔɡ]

(noun.) largest North American frog; highly aquatic with a deep-pitched voice.

Edited by Angus--From WordNet

(n.) A very large species of frog (Rana Catesbiana), found in North America; -- so named from its loud bellowing in spring.

Edited by Ian