Fairlead
From MITNA
A block, padeye, ring or any other fitting which controls the path of a line on a boat.
When a line is not running correctly where it is supposed to go, or is snagged or stuck, it is said to be "fouled". When a line is running correctly and is not fouled, it is said to be "fair".
A fairlead is simply a device that "leads" a line "fair".