Definition of "fathead"

(derogatory) An idiot; a fool.  quotations  examples

A cyprinid fish of the Mississippi valley, Pimephales promelas, the black-headed minnow.  examples

A labroid food fish of California; the California sheephead. Semicossyphus pulcher.  examples

A blobfish, Psychrolutes microporos  examples

Any of several species of fish of the genus Cubiceps  examples