one of a group of organic compounds, secreted by an ascomycetous fungus (Gibberella fujikuroi), which behave like plant hormones in stimulating seed germination, growth of roots, leaves, and stems, etc.
See gibberellin in American Heritage Dictionary 4
(jĭbˌə-rĕlˈĭn)
noun
Any of several plant hormones, such as gibberellic acid, used to promote stem elongation.