Of a manner of speaking or writing: without affectation, with ease.

Spontaneously; without art or artifice. Now rare.

In a careless manner, without care; without apprehension (obsolete); without attention, art, or study; (now esp.) heedlessly, thoughtlessly…

In a sincere or honest manner; without guile or deceit; openly. Also: unaffectedly, artlessly; in a natural manner. Now somewhat rare.

In an unaffected manner; without affectation.

In an artless or unaffected manner; simply, artlessly.

Esp. in art and performance arts: in a way that is suggestive of nature; naturally, realistically. Cf. naturalistically, adv.

(un-, prefix1 affix 5.)