burst into

1. Also, burst out in or into . Break out into sudden activity. For example, burst into flames means "break out in a fire," as in This dry woodpile may well burst into flames. A version of this term, which dates from the 16th century, was used figuratively by John Milton: "Fame is the spur ... But the fair guerdon [reward] when we hope to find, and think to burst out into sudden blaze" ( Lycidas, 1637).

2. Also, burst out. Give sudden utterance to. For example, burst into tears or laughter or song or speech or burst out crying or laughing or singing , etc. mean "begin suddenly to weep, laugh, sing," and so on, as in When she saw him, she burst into tears, or I burst out laughing when I saw their outfits, or When they brought in the cake, we all burst into song. These terms have been so used since the late 1300s.