Any of a number plant growth hormones, the first of which was isolated in 1938 from the fungus Gibberella fujikuroi; more than 60 related gibberelins are known. The most important is gibberellin A₃, also called gibberellic acid. They are used in agriculture for promoting plant growth. [WordNet 1.5]

top

OXFORD DICTIONARY

gibberellin, n. one of a group of plant hormones that stimulate the growth of leaves and shoots.

Etymology

Gibberella a genus of fungi, dimin. of genus-name Gibbera f. L gibber hump

For further exploring for "gibberellin" in Webster Dictionary Online