grin1 [intransitive] past tense and past participle grinned, present participle grinning
to smile widely
She grinned at me, her eyes sparkling.
He walked out of the pool, grinning widely.
He was grinning like an idiot (=grinning in a silly way).
grin from ear to ear (=grin very widely)
to accept an unpleasant or difficult situation without complaining, usually because you realize there is nothing you can do to make it better