Answer: cocksure

AnswerCrossword Clue
COCKSUREInsufferably confident
COCKSUREArrogantly positive
COCKSUREAbsolutely positive.
COCKSUREToo self-confident.
COCKSURESelf-confident to an offensive degree.
COCKSUREOverconfident
cocksurecertain (absolutely confident)
cocksuretoo certain; overconfident
cocksureperfectly sure or certain; completely confident in one's own mind
cocksureArrogantly or presumptuously overconfident.