Dictionary.net

• A slope or declivity in a manege ground down which a horse is made to gallop, to give suppleness to his haunches.

2010 - New Age Dictionary Database
By Oddity Software

• A slope or declivity in a manege ground down which a horse is made to gallop, to give suppleness to his haunches.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.