Gainsaying(verb)
Question the truth or validity of; take exception to; Deny or contradict;
Hindi meaning:चुनौती देना
Synonyms: Dent, Contravene, Disclaim, Challenge
Antonyms: Accept, Acknowledge, Admit
Example: She gainsaid his claims.
Forms: Gainsays, Gainsaying, Gainsaid
Trick to remember: Gain hi hota hai teacher ko bi agar koi Gainsaying karta hai toh. 
