Bouncing bulbs are bouncing eggplant like fruit. They are quite aggressive and must be withered with Incendio before attempting to pick them up.
Harry was hit in the face by a bouncing bulb when he tried to pick it up.
First years learn to use Incendio on bouncing bulbs to shrink them and put them back in the crate for professor Sprout.
Hermione once overheard a scandalous story in the three broomsticks about a witch, a warlock and a sack of bouncing bulbs.
Bouncing bulbs can be eaten like aubergines/eggplants.