DCCa long looseshirt that someone, especially a man, wears in bed 〔男用〕衬衫式长睡衣
Examples from the Corpus
nightshirt• Her sensiblecottonnightshirt must have been one of his discards.• Polly turned the deadlock, and before reaching for the latchdabbed at her eyes with the hem of her nightshirt.• She got up from the bed, buttoned up her nightshirt and went to the door.• And picking up her nightshirt from under the pillow, she went into the bathroom.