Certifiable is one of those interesting words which has two meanings that are completely opposed.
On the one hand, certifiable means to be mentally ill or without the ability to make logical and sensible decisions. The person could be certified as crazy in a mental institution.
On the other hand, certifiable may also mean the person or object is able to be certified, or able to be deemed real or genuine. The teacher who is ready to take his certification exam is certifiable. The large ruby is certifiable; it is real.
The adverb form of this word is certifiably.
Examples
There’s much more certifiable lunacy: in these days of mobiles, Khushi does not know that Vishi has gone to Bangkok in place of Jackson, and Jackson too does not know about her existence – talk of taking girlfriends for granted. [India West]
It’s hard to read the news and not be discouraged. Were he to internalize it all, he says, “I’d be certifiable.” We would all be. It would be bleak. [Sacramento Bee]
But with winter approaching, when only the certifiably lunatic frostbiters will be out on the water, I began to think about whether Annapolis deserves its self-annointed “Sailing Capital” status. [Capital Gazette]
Langford has been a revelation this year, and wasn’t remotely daunted by the big occasion, laying six tackles and scoring three goals, two of them certifiable classics: one glorious strike on the run at the end of a mesmerising cat’s cradle of handballs, one conjuring trick from an absurd angle in the forward pocket. [The Guardian]