There are numerous synonyms for the phrase "crack a smile." Some of the most commonly used ones include "grin," "beam," "smirk," "smile," "chuckle," "laugh," "smile broadly," "beam widely," "flash a grin," "smile widely," "grin from ear to ear," and "burst out laughing." Each of these phrases convey the same basic idea of someone smiling or laughing in response to something humorous or enjoyable. These synonyms can be used interchangeably depending on the context and the tone of the communication. Whether it's in a casual conversation or a formal setting, there's a synonym to convey the exact emotion.