From Longman Dictionary of Contemporary Englishbe burstingbe burstinga) British English informalHBH to need to go to the toilet very soon b) (also be bursting at the seams) to be so full that nothing else can fit inside → burst
Examples from the Corpus
be bursting• The shells were bursting...• By the time I got into position, my lungs were bursting and I had to go up for air again.• As it is, the Shishu Bhawans seem to be bursting at their seams.• Sure enough, the enemy mortars were bursting in the fields on both sides of the road.• Once again she was bursting into tears over nothing at all.• She was bursting to relieve herself, but even though that was what was wanted of her, she couldn't.• His entire back was bursting with fluids at the end of that day.• Well Loaded are bursting with life and enough youth to get refused service at the bar. 