a narrow strap of leather attached to each end of the bit in the mouth of a horse, and held by the rider or driver to control the animal: usually used in pl.
a means of guiding, controlling, checking, or restraining: the reins of government
transitive verb
to guide, control, check, or restrain with or as with reins
intransitive verb
to stop or slow down a horse, etc. with or as with reins: with in or up
Archaic to submit to or be controlled by reins: said of a horse