na-adjective
cheerful and openhearted; bright and magnanimous
Describes a personality that is upbeat, frank, and generous in spirit. Often used to characterize someone's disposition or attitude.
彼は明朗闊達な性格で、誰とでもすぐに仲良くなれる。
He has a cheerful and openhearted personality, and can quickly become friends with anyone.
明朗闊達に振る舞うことで、周囲の雰囲気も明るくなる。
By behaving in a bright and magnanimous way, you can lighten the mood around you.
A yojijukugo combining 明朗 (bright, cheerful) and 闊達 (openhearted, magnanimous). The exact historical derivation is uncertain, but the compound is conventionally used to describe a cheerful and generous personality.