If you tether an animal or object to something, you attach it there with a rope or chain so that it cannot move very far. The officer dismounted, tethering his horse to a tree. to tie an animal to a post so that it can only move around within a limited area
If you say that you are at the end of your tether, you mean that you are so worried, tired, and unhappy because of your problems that you feel you cannot cope. She was jealous, humiliated, and emotionally at the end of her tether
Attached to a belt and then to a ladder or some other fixed point at poolside, a tether helps you turn a too-small pool into a swimmer's treadmill For example, you can have a great workout in a hotel pool or any other pool that's too small for laps