adverb, adverb taking the 'to' particle
with a meaningful grin; suggestively; sneeringly
Describes a brief, knowing, or suggestive smile, often with a hint of satisfaction, mischief, or scorn. Typically used with 笑う or する.
He grinned meaningfully as if he knew the secret.
犯人は刑事の質問にニヤリとするだけだった。
The suspect just smirked at the detective's question.
He gave a knowing smirk and wouldn't tell me the answer.
Realizing she knew the secret, she gave a sly smirk.
The criminal's mouth twisted into a sly grin.