The definition of a tether is a leash or restraint that inhibits free movement or actions.(noun)
The rope that you use to tie your dog to a tree is an example of a tether.
To tether is to tie an animal up or to do something that restricts freedom.(verb)
When you tie your dog to a tree, this is an example of a situation where you tether your dog.
See tether in Webster's New World College Dictionary
Origin: ME < ON tjōthr, akin to OHG zeotar, wagon shaft
See tether in American Heritage Dictionary 4
Origin: Middle English tedir, tethir
Origin: , from Old Norse tjōdhr.
Learn more about tether