n. 后部撑物

[ noun ]
a stay that supports the back of something
<noun.artifact>

Backstay \Back"stay`\ (b[a^]k"st[=a]`), n. [Back, a. or n. +
stay.]
1. (Naut.) A rope or stay extending from the masthead to the
side of a ship, slanting a little aft, to assist the
shrouds in supporting the mast. [Often used in the
plural.]

2. A rope or strap used to prevent excessive forward motion.