Meanings of lose a stirrup in English

Glancing backward I saw him lose a stirrup and fall and pick himself up and run as if his life depended on it.

I lost a stirrup, and the devil of a horse threw me.

Very few amateur riders cope well with losing a stirrup in mid-race.

For a moment he was in the air as his uncle cried, You lost a stirrup.

You lost a stirrup when Dixy shied.

Twice she lost a stirrup and grabbed the saddle horn to save herself from going over his head.

Call was riding along relaxed and, before he could even jerk her head up, he lost a stirrup and knew he was thrown.

Milon struck his adversary so fiercely, that the lance splintered in his gauntlet; but the young knight kept his seat without even losing a stirrup.