Boy's play

childish amusements; anything trifling.

See also: Boy

References in classic literature ?
Man does some of his part of the exchange work in his six weeks of haying, and it is no boy's play.
But pretty soon, he undertook an affair that made all his foregone adventures seem like mere boy's play.
She was fond of all boy's plays, and greatly preferred cricket not merely to dolls, but to the more heroic enjoyments of infancy, nursing a dormouse, feeding a canary-bird, or watering a rose-bush.