Sinker \Sink"er\, n. One who, or that which, sinks. Specifically:
   (a) A weight on something, as on a fish line, to sink it.
   (b) In knitting machines, one of the thin plates, blades, or other devices, that depress the loops upon or between the needles.

Dividing sinker, in knitting machines, a sinker between two jack sinkers and acting alternately with them.

Jack sinker. See under Jack, n.

Sinker bar.
   (a) In knitting machines, a bar to which one set of the sinkers is attached.
   (b) In deep well boring, a heavy bar forming a connection between the lifting rope and the boring tools, above the jars.

Source: Webster's Revised Unabridged Dictionary (1913)