Water sprout

Water sprout: A vigorous upright shoot from an adventitious or latent bud on the trunk or main branch of a tree. Also known as a sucker, a vertical shoot growing from the main trunk or branches. 

A vigorous shoot originating above ground on a plant's trunk, older wood, or bud union. Usually breaks from a latent bud. Often the result of heavy pruning.

In horticulture, a vigorous, sappy, adventitious shoot in a tree or bush, usually arising because of heavy pruning or other unbalance of the plant.