1.
If you burst into tears, laughter, or song, you suddenly begin to cry, laugh, or sing.
She burst into tears and ran from the kitchen.
...books that cause adults to burst into helpless laughter.
PHRASAL VERB : V P n , V P n
2.
If you say that something bursts into a particular situation or state, you mean that it suddenly changes into that situation or state.
This weekend’s fighting is threatening to burst into full-scale war...
PHRASAL VERB : V P n
3.
to burst into flames: see flame