1
general::
Having a very high opinion of oneself, filled with or showing excessive self-esteem. For example, She strutted about in her new outfit, proud as a peacock. This simile alludes to the male peacock, with its colorful tail that can be expanded like a fan, which has long symbolized vanity and pride. Chaucer used it in The Reeve's Tail: "As any peacock he was proud and gay." [1200s]
American Heritage Idioms
2
general::
Phrase(s): *proud as a peacock [and] *vain as a peacock
overly proud; vain. (*Also: as ~.) • Mike’s been strutting around proud as a peacock since he won that award. • I sometimes think Elizabeth must spend all day admiring herself in a mirror. She’s as vain as a peacock.
McGrawhill's American Idioms And Phrasal Verbs