Appropriate for celebration; joyous or auspicious (used for happy occasions or fortunate events).
結婚式はみんなにとっておめでたい日だ。
A wedding is a joyous day for everyone.
昇進の知らせで社内はおめでたい雰囲気に包まれた。
The office was wrapped in a celebratory mood after the promotion news.
おめでたい席では黒い服は避けた方が良い。
It's better to avoid wearing black at celebratory occasions.
Naive or overly simple-minded; gullible or foolish (used to describe someone who is easily pleased or easily deceived).
そんな話をすぐ信じるなんておめでたい人だね。
You're so gullible to believe a story like that right away.
彼はおめでたい性格で、悪い知らせでもすぐ忘れてしまう。
He has such a simple, happy-go-lucky personality that he quickly forgets bad news.
今回の成功で彼はおめでたい誤解をしている気がする。
I feel he has a rather naive misconception because of this success.