Wordnet 3.0
ADJECTIVE (2)
1. 
 fit to be certified as insane (and treated accordingly); 
[syn: certifiable, certified]
2.  capable of being guaranteed or certified; 
- Example: "a certifiable fact"
The Collaborative International Dictionary of English v.0.48:
certifiable \certifiable\ adj.
   1. presenting symptoms of mental illness sufficient for legal
      commitment to a mental institution.
   Syn: certified.
        [WordNet 1.5]
   2. capable of being guaranteed or certified: a certifiable
      fact.
      [WordNet 1.5]
WordNet (r) 3.0 (2006):
certifiable
    adj 1: fit to be certified as insane (and treated accordingly)
           [syn: certifiable, certified]
    2: capable of being guaranteed or certified; "a certifiable
       fact"