(1):

(v. t.) To insert a rowel, or roll of hair or silk, into (as the flesh of a horse).

(2):

(n.) The little wheel of a spur, with sharp points.

(3):

(n.) A roll of hair, silk, etc., passed through the flesh of horses, answering to a seton in human surgery.

(4):

(n.) A little flat ring or wheel on horses' bits.