One who sinks something.

(fishing) A weight used in fishing to cause the line or net to sink.

(baseball) Any of several high speed pitches that have a downward motion near the plate; a two-seam fastball, a split-finger fastball, or a forkball.

(construction) A sinker nail, used for framing in current construction.

(slang) A doughnut; a biscuit.

In knitting machines, one of the thin plates, blades, or other devices, that depress the loops upon or between the needles.