also: ナルシシスティック
na-adjective
narcissistic
A loanword from English, used as a な-adjective to describe someone who is excessively self-admiring or self-centered. Often used in psychological or casual contexts.
彼はナルシスティックな性格で、いつも自分の話ばかりする。
He has a narcissistic personality and always talks only about himself.
SNSに自撮りをたくさん投稿するのは、少しナルシスティックだと思う。
I think posting a lot of selfies on social media is a bit narcissistic.
ナルシスト is a noun meaning 'narcissist' (a person), whereas ナルシスティック is an adjective describing the behavior or personality.
Borrowed from English 'narcissistic', ultimately from the Greek myth of Narcissus.