Checkrein

1. n. A branch rein connecting the driving rein of one horse of a span or pair with the bit of the other horse.
2. n. A short rein looped over the check hook to prevent a horse from lowering his head; — called also a bearing rein.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.