maniacal

1. Suggestive of or afflicted with insanity: a maniacal frenzy.
2. Characterized by excessive enthusiasm or excitement: a maniacal interest in gambling.

adjective

Afflicted with or exhibiting irrationality and mental unsoundness: brainsick, crazy, daft, demented, disordered, distraught, dotty, insane, lunatic, mad, maniac, mentally ill, moonstruck, off, touched, unbalanced, unsound, wrong. Informal bonkers, cracked, daffy, gaga, loony. Slang bananas, batty, buggy, cuckoo, fruity, loco, nuts, nutty, screwy, wacky. Chiefly British crackers. Law non compos mentis. Idioms: around the bend, crazy as a loon, mad as a hatter, not all there, nutty as a fruitcake, offout ofone's head, off one's rocker, of unsound mind, out of one's mind, sick in the head, stark raving mad. See sane/insane.

Suggestive of or afflicted with insanity.

The adjective has one meaning:

Meaning #1: wildly disordered
  Synonym: maniac