From Longman Dictionary of Contemporary Englishbe bursting to do somethingbe bursting to do somethinginformalWANT to want to do something very much Zach was bursting to tell them something. → burst
Examples from the Corpus
be bursting to do something• The vast reservoir of information he had acquired was bursting to be expressed.• She was bursting to relieve herself, but even though that was what was wanted of her, she couldn't.• They were bursting to tell her things she would never know. 