Being in good health; robust. Often used in greetings or to wish long life, especially for older people.
お達者でお過ごしください。
Please stay well (used as a polite farewell/wish for health).
祖父は90歳になっても達者だ。
My grandfather is robust even at 90 years old.
Skilled; proficient; adept — having superior ability in a certain area.
彼女は料理が達者だ。
She is skilled at cooking.
彼は達者に箏を弾いた。
He played the koto skillfully.
A master or expert; a person outstanding in a particular skill or field.
彼は剣術の達者として知られている。
He is known as a master of swordsmanship.