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2.
(adj) Completely NUTS. Past the point of "ticking". Ready to flip OUT.
Oh shit! That chick's been off her meds for a few days now! She's certifiable!
by starlight88 February 04, 2010
 
1.
British slang for "insane". Derived from "certifiably insane".
The evil genius villains in James Bond movies appear to be highly intelligent when, in actuality, they are certifiable.
by little scottie October 07, 2005