a barbed hook, usually metal, used for fishing
a jack (the playing card)
a rope, cable etc. that holds something in place whilst allowing some movement
a strong rope or line that connects a sailor's safety harness to the boat's jackstay
the limit of one's abilities, resources etc.
The cardinal number three in an old counting system used in Teesdale and Swaledale. (Variant of tethera)
to connect something to something else.
to connect a cellular smartphone to another personal computer in order to give it access to a hotspot.
to restrict something with a tether.