sceptical
cynical, disbelieving, doubtful, doubting, dubious, hesitating, incredulous, mistrustful, questioning, quizzical, scoffing, take with a pinch of salt, unbelieving, unconvinced
Antonyms
believing, certain, convinced, credulous, dogmatic, free from doubt, of fixed mind, sure, trusting, undoubting, unquestioning