To draw tighter; to straiten; to make more close in any manner.

make tight or tighter; "Tighten the wire"

become tight or tighter; "The rope tightened"

The act of rising the rod tip quickly to straighten the line and apply tension to it, in order to sink the hook into the mouth of a taking fish.

narrow or limit; "reduce the influx of foreigners"

restrict; "Tighten the rules"; "stiffen the regulations"