grin from ear to ear
US /ɡrɪn frəm ɪr tu ɪr/
UK /ɡrɪn frəm ɪr tu ɪr/
1.
to smile broadly, showing great pleasure or amusement
:
•
When she saw the surprise party, she started to grin from ear to ear.
•
He was grinning from ear to ear after winning the lottery.