expert; master; skilled person
Refers to a person who has attained a high level of skill or mastery in a particular field. Somewhat literary or formal in tone.
彼は茶道の達士として知られている。
He is known as a master of the tea ceremony.
その達士の技は見事だった。
The expert's skill was splendid.
The word is composed of 達 (attainment, mastery) and 士 (person of skill, gentleman). The exact historical derivation is uncertain, but the combination naturally suggests a person who has achieved mastery.