n.
   - a control or limit:![]()  curbs on cigarette advertising. ▸
(also curb bit)
 a type of bit with a strap or chain attached which passes under a horse's lower jaw, used as a check. 
- N. Amer. variant spelling of kerb.
- a swelling on the back of a horse's hock, caused by spraining a ligament.
v.
 keep in check; control.
Etymology
  C15: from OFr. courber ‘bend, bow’, from L. curvare (see curve).