crack a smile
To smile. I got the baby to crack a smile by clapping and singing.
crack a smile
to grin; to smile. I was tellin' my best jokes, but Jim never cracked a smile. She looked surprised, and then cracked a big, beautiful smile.
crack a smile
Smile, as in Betty was a very serious person; she rarely cracked a smile. This colloquialism transfers crack in the sense of "break" to breaking a serious facial expression into a smile.