rooter

One who roots for the success of his patron or his side; specifically, in base-ball and other outdoor contests, one who gives aid and encouragement to his side by applause and by shouting advice.

One who or that which roots or roots up, or tears up by the roots; one who eradicates or destroys.

A plant (or, figuratively, some other thing, or a person) which takes root.

One who, or that which, roots; one that tears up by the roots.

One who roots, or applauds.

One who, or that which, roots; one that tears up by the roots.

an enthusiastic devotee of sports