Unbackable

A horse which is quoted at short odds that punters decide is too short to return any reasonable amount for the money they outlay.

Underlay

A horseracing at shorter odds than seems warranted by its past performances.

Under Starters Orders

The starting of a race (also referred to as Under Orders).

Under Wraps

A horse under stout restraint in a race or workout.

Value

Getting the best odds on a wager.

Wager

Another term for a bet.

Walkover

A race in which only one horse competes.

Warming Up

Galloping a horse on the way to post.

Weigh In/Out

Weigh In/Out - The certification, by the clerk of scales, of a rider's weight before/after a race. A jockey weighs in fully dressed with all equipment except for his/her helmet, whip and (in many jurisdictions) flak jacket.

Weight-For-Age

A practice that allows horses of different age and sex to compete on equal terms. The weight a horse carries is allocated on a set scale according to its sex and age.

Wire

The finish line for a race.

Yearling

A horse in its second calendar year of life, beginning January 1st of the year following its birth.

Yielding

Condition of a turf course with a great deal of moisture. Horses sink into it noticeably.