gullible

Synonyms: being a sucker believing biting credulous easily taken in easy mark falling hook line and sinker foolish green innocent kidding oneself mark silly simple sucker susceptible swallowing whole taken in taking the bait trustful tumbling for unskeptical unsophisticated unsuspecting wide-eyed

Antonyms: astute discerning knowledgeable perceptive suspicious unbelieving untrusting wise