A crack or fissure in the hoof of the horse, occurring usually on the inside of the forefoot (quarter-crack) or in the forepart of the hindfoot (toe-crack); when the crack is deep enough to expose the sensitive laminae, or when it extends to the coronary band, lameness results. ... (05 Mar 2000) ... 
[n] - a fissure in the wall of a horse`s hoof often causing lameness
noun a fissure in the wall of a horse`s hoof often causing lameness