na-adjective, noun
free and easy; open-hearted; relaxed; frank
Describes a person's character or manner as unpretentious, broad-minded, and not overly concerned with formalities or small details. Often used positively for someone who is easygoing and straightforward.
彼は洒落な性格で、誰とでもすぐ仲良くなる。
He has a free and easy personality and quickly becomes friends with anyone.
洒落に構えて、細かいことは気にしない。
Take it easy and don't worry about the small stuff.
The exact derivation is uncertain. The kanji 洒 (wash, cleanse) and 落 (drop, fall) may suggest a sense of being cleansed of petty concerns, but this is speculative.