Throw-off

We had not covered much more than three miles since the throw-off; but horses and hounds already exhibited a most interesting and picturesque tail.

Source: wiktionary

The sixty horsemen spread away for the start, the two pretty Amazons set their lips, a mob of peasants in blue blouses form a noisy fringing to the phaetons and barouches which have come to see the throw-off, and conspicuous amidst all this we have M. Pistache's roan, which, unable to stand the music of the horns, first jumps, then pivots on its hind legs, then springs off like a shot, well-nigh wrenching M. Pistache's arms out of their sockets.

Source: wiktionary

The 'throw-off' was at one o'clock, and the gallop lasted more than two hours and a half, so that the fox had a very long run.

Source: wiktionary

On one occasion the meet was at Boughton House, the seat of the Duke of Buccleuch, when, just before the throw-off, the keeper requested Mr. Smith to come with him to see a curious matter.

Source: wiktionary