na-adjective, noun
Describes a natural, uncontrived quality in art, writing, or behavior, free from excessive technique or affectation. Often used positively to suggest genuine simplicity.
彼の文章は無技巧で、かえって心に響く。
His writing is artless, and that makes it all the more moving.
無技巧な演奏が、聴衆に深い
The simple, unaffected performance deeply moved the audience.
自然 is a broader term for naturalness; 無技巧 specifically implies a lack of contrived skill or technique.
Compound of 無 (without) and 技巧 (technique, skill). The word is a straightforward Sino-Japanese formation.