All 6 Uses

mischievous
in
Another Country
(Auto-generated)

Her eyes were now very bright and mischievous and she looked like a little girl.†
p. 17.2
She held a drink and a cigarette in one hand and looked at once like the rather weary matron she actually was and the mischievous girl she once had been.†
p. 73.9 *
Her face, then, made one think of a mischievous street boy.†
p. 103.8
She gave them a quick, mischievous grin, and whispered, "But they seem so silly-!†
p. 151.7
Then he grinned, mischievously.†
p. 220.7

mischievously = in a manner that playfully causes minor trouble
It did not contain the mischievous delight that he remembered.†
p. 233.9

Definitions:

(1) (mischievous)
playfully causing minor trouble; or describing the smile of someone doing so

Much less commonly, mischievous can reference real harm without any sense of fun. But in modern writing, that usage has largely shifted to other words like malicious, destructive, or damaging.
(2) (meaning too rare to warrant focus)
In law, mischievous references a property crime such as vandalism or graffiti. Very rarely, the word can reference someone or something causing serious damage.

In archaic literature mischievous often refers to bad behavior without any connotation of playfulness or of the harm being minor.