screw loose
Not quite right
Someone with a screw loose is mentally unstable or eccentric—their mind isn't quite fastened together properly.
The phrase usually appears with have: He's got a screw loose if he thinks that'll work.
It's informal and mildly dismissive rather than clinical, suggesting odd behavior more than serious mental illness.
- mad as a hatterCompletely, absurdly insane
- bonkersWildly irrational, unhinged
- crazyMentally unhinged
- insaneSeverely mentally disturbed
- not all thereMentally deficient somehow
deranged · loony · round the bend · screwy · batty · eccentric · cracked · twist · unhinged · off the rails · nutcase · nut · off-kilter · out to lunch · lost the plot · bolt · off one's rocker · mad
screw loosesane
Mentally healthy, clearheaded
of sound mind · all there · stable · well-adjusted · balanced
screw loosesharp
Fine-edged, or astute
sharp as a tack · quick-witted · lucid · astute · keen
screw loosenormal
Conforming to standard
conventional · well-grounded · sensible · reasonable · down-to-earth