Real Dictionary

root
The roots of a plant are the parts of it that grow under the ground.
verb: If you root a plant or cutting or if it roots, roots form on the bottom of its stem and it starts to grow.

Root in American English
Elihu1845-1937; U.S. statesman: secretary of state (1905-09)

root in American English 1
the part of a plant, usually below the ground, that lacks nodes, shoots, and leaves, holds the plant in position, draws water and nourishment from the soil, and stores food
noun: a part of the body of a plant that develops, typically, from the radicle and grows downward into the soil, anchoring the plant and absorbing nutriment and moisture

root in American English 2
to dig in the ground, as with the snout
to dig or turn (up or out) with or as with the snout
intransitive verb: to turn up the soil with the snout, as swine
transitive verb: to turn over with the snout

root in American English 3
intransitive verb: to encourage a team or contestant by cheering or applauding enthusiastically

root in British English 1
noun: the organ of a higher plant that anchors the rest of the plant in the ground, absorbs water and mineral salts from the soil, and does not bear leaves or buds

root in British English 2
(of a pig) to burrow in or dig up the earth in search of food, using the snout

root in British English 3
verb: to give support (to a contestant, team, etc), as by cheering