adv

• (horse racing) Without any weight restrictions; without being handicapped.
  "They'll break from the gate in full tack with jockeys riding catchweight in silks."

adj

• (sports) Without any weight restrictions; having no handicap.
  "There were also races for gentlemen-riders, in whch all the best performers of the day took part. Lord Glamis, afterwards Earl of Strathmore, rode his maiden race there—a catchweight match with Sir Watkin Wynn, a rare bit of fun got up by the officers of the 1st Life Guards."

noun

• (sports) A weight category other than the standard weight categories: either an agreed-upon weight range or an agreement to allow any weight.
  "There was an especially good entry, thirty-nine horses, representing twenty-two regiments, being entered in the Light Weight race, which was for horses five years old and upwards, the property of oflicers on full or half pay of the Regular Army, that had not won a race under the recognised rules of steeplechasing in any country, point-to-point races excepted; while eighteen faced the starter in the Welter race, in which the conditions were the same, excepting that the catchweight was 13 st. 7 lb."