nutso /ˈnʌt.soʊ/adjective 4adverb 2noun 2forms 3 adjective4 •(informal) Crazy, insane."You wanted a report, so here's a full report: crazy, nutso, raisins short of a fruitcake, rubber walls, screaming-mad basket-cases." — 2000 •(informal) Ridiculous; unbelievable or silly.Trust me, we both can find fringe fanatics to prove the other side is nutso. So let's stop with this stereotypical silliness. — 2008 •(informal) Obsessed; overly enthusiastic.Even the most nutso fisherman would think twice about going out on the lake today. — 2001 •(informal) Fraught or out of control.How being taught to not cut corners, even in a nutso emergency room shift, meant I checked all regions in Mary below the waist and didn't just tell her I thought it was probably gas. — 2005 adverb2 •(informal) In a crazy manner.In there was Captain Ed Cutler, whom every man and woman in Maggie's old command had once seen run nutso in Valhalla. — 2014 •(informal) Madly; extremely or obsessively.I'm completely, utterly, nutso in love with that man! — 2012 noun2 •(informal) A crazy person; a crackpot or lunatic.Sadly, at the end of his life, Luther became somewhat of a nutso. — 2012 •(informal) Craziness; insanity.I wrote a letter to the Guild Newsletter apologizing for having disrupted the show, pleading temporary nutso. — 2012 formsnutsos · more nutso · most nutso