The "healthy" alternative to a "burger" or chicken clumps; a sandwich comprised of some sort of a fried fishy patty on a bun with an enormous dollop of mayo-AYO, available at McDonald's.
by Stu E. January 09, 2008

That sandwich at McDonald's purportedly made of "fish"...my guess is it is white rubber with mayo on bread. Also known as the Fillet-o-Fish.
by gourmet consumer January 07, 2009
