Thesaurus.com
Dictionary.com
Definitions

screw loose

ADJECTIVE
crazy
Synonyms
STRONGEST
insane kooky mad nuts nutty silly wacky
STRONG
ape berserk cuckoo lunatic potty psycho screwball
WEAK
barmy bats in the belfry batty bonkers cracked crazed daft delirious demented deranged dingy dippy erratic flaky flipped flipped-out freaked-out fruity idiotic mad as a March hare mad as a hatter maniacal mental moonstruck nutty as fruitcake of unsound mind out of one's mind out of one's tree out to lunch round the bend screwy touched unbalanced unglued unhinged unzipped
Antonyms
STRONGEST
balanced calm collected rational reasonable sane sound
WEAK
realistic responsible sensible

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

I suppose there is a Screw loose in me on that point, seeing what all thinking People think of it. 

From Letters of Edward FitzGerald to Fanny Kemble (1871-1883) by Wright, William Aldis

Screw loose in the chart perhaps—something certainly wrong somewhere—but here we were with breakers ahead, my lads, driving head on, slap on a lee shore! 

From The Uncommercial Traveller by Dickens, Charles