A person who is ardently devoted to a particular subject or activity:bug, devotee, enthusiast, fanatic, zealot. (Informal) buff2, fan2, fiend. (Slang) freak, nut. See concern adjective
Afflicted with or exhibiting irrationality and mental unsoundness:brainsick, crazy, daft, demented, disordered, distraught, dotty, insane, lunatic, mad, maniacal, 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, off (or out of) one's head, off one's rocker, of unsound mind, out of one's mind, sick in the head, stark raving mad. See sane Roget's II The New Thesaurus Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.