Definition of "windsucking"

Wind-sucking bears a close analogy with Crib-biting […], it arises from the same causes, and the same results follow. The Horse stands with his neck bent, his head drawn inward, his lips alternately a little opened and then closed, and a noise is heard as if he were sucking […]. It is a Vice.

1847, George Henry Hewit Oliphant, “III. [Diseases, Defects or Alterations in Structure, and Bad Habits.]”, in The Law Concerning Horses, Racing, Wagers and Gaming; with an Appendix Containing Recent Cases, Statutes, &c., London: S[tephen] Sweet, 1, Chancery Lane, law bookseller and publisher, page 62

Cribbing is scarcely a disease, though it may be productive of disease of the larynx. It is a habit usually acquired by young horses, either in idle moments or by imitation, often from the dam. The colt takes any wooden substance, such as a paling or manger, between his teeth and gnaws it. From that he proceeds to inhale the air, and often, when this habit has been acquired, he becomes a windsucker. It is probable that windsucking produces irritation in the throat and air-passages, and may lead to some enlargement, and consequently to roaring; but it is more probable that windsucking is the effect of disease.

1892, [Frederick Tynte] Warburton, “Accidents and Diseases”, in The Race Horse: How to Buy, Train, and Run Him, London: Sampson Low, Marston & Company Limited, St. Dunstan's House, Fetter Lane, Fleet Street, E.C., page 261