great white heron n 1: a common egret of the genus Egretta found in America; it is a variety of the Old World white egret Casmerodius albus [syn: {American egret}, {great white heron}, {Egretta albus}] 2: widely distributed Old World white egret [syn: {great white heron}, {Casmerodius albus}] 3: large white heron of Florida and the Florida Keys [syn: {great white heron}, {Ardea occidentalis}]