Incredible, a.
Etymology: [L. incredibilis: cf. OF. incredible. See In- not, and Credible.]
Not credible; surpassing belief; too extraordinary and improbable to admit of belief; unlikely; marvelous; fabulous. Why should it be thought a thing incredible with you, that God should raise the dead Acts xxvi. 8.
Shades of meaning
Fernald lists incredible only as an antonym, under likely.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given