Definition of shoe-in:
(n) :
(footwear) A protective covering for the foot, with a bottom part composed of thick leather or plastic sole and often a thicker heel, and a softer upper part made of leather or synthetic material. Shoes generally do not extend above the ankle, as opposed to boots, which do.
(n) :
A piece of metal designed to be attached to a horse's foot as a means of protection; a horseshoe.
(n) :
(card games) A device for holding multiple decks of playing cards, allowing more games to be played by reducing the time between shuffles.
(v) :
(transitive) To put shoes on someone or something else's feet, especially to put horseshoes on a horse.
(v) :
(intransitive) To put shoes on one's own feet.
(n) :
(by extension, slang) A pneumatic tire, especially for an automobile.