The dog had broken loose from its tether and was running around in the yard.
2 tie (up or down), restraint, fetter, chain (up or down), leash, manacle, secure, shackle, fasten, picket, stake:
Why don't you tether the goat where the grass is more plentiful?
Advanced English Dictionary
verb, noun +verb[VN] ~ sth (to sth) to tie an animal to a post so that it cannot move very far: He tethered his horse to a tree. +noun a rope or chain used to tie an animal to sth, allowing it to move around in a small area Idioms see END n.
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