Inconceivable(adjective)
Difficult to believe, or unlikely.
Hindi meaning:असंभव; अकल्पनीय
Synonyms: Improbable, Questionable, Unconvincing, Implausible
Antonyms: Tenable, Feasible, Reasonable, Cogent
Example: The whole plot of the film is ridiculously inconceivable.
Trick to remember: In(not)conceivable sounds like not imaginable/believable. 
