What is "to be on the rack"

Rack \Rack\, n. [Probably fr. D. rek, rekbank, a rack, rekken to stretch; akin to G. reck, reckbank, a rack, recken to stretch, Dan. r[ae]kke, Sw. r["a]cka, Icel. rekja to spread out, Goth. refrakjan to stretch out; cf. L. porrigere, Gr. 'ore`gein. [root]115. Cf. Right, a., Ratch.]

1. An instrument or frame used for stretching, extending, retaining, or displaying, something. Specifically:

   1. An engine of torture, consisting of a large frame, upon which the body was gradually stretched until, sometimes, the joints were dislocated; -- formerly used judicially for extorting confessions from criminals or suspected persons.

      During the troubles of the fifteenth century, a rack was introduced into the Tower, and was occasionally used under the plea of political necessity.
      --Macaulay.

   2. An instrument for bending a bow.

   3. A grate on which bacon is laid.

   4. A frame or device of various construction for holding, and preventing the waste of, hay, grain, etc., supplied to beasts.

   5. A frame on which articles are deposited for keeping or arranged for display; as, a clothes rack; a bottle rack, etc.

   6. (Naut.) A piece or frame of wood, having several sheaves, through which the running rigging passes; -- called also rack block. Also, a frame to hold shot.

   7. (Mining) A frame or table on which ores are separated or washed.

   8. A frame fitted to a wagon for carrying hay, straw, or grain on the stalk, or other bulky loads.

   9. A distaff.

2. (Mech.) A bar with teeth on its face, or edge, to work with those of a wheel, pinion, or worm, which is to drive it or be driven by it.

3. That which is extorted; exaction. [Obs.]
   --Sir E. Sandys.

   Mangle rack. (Mach.) See under Mangle. n.

   Rack block. (Naut.) See def. 1 (f), above.

   Rack lashing, a lashing or binding where the rope is tightened, and held tight by the use of a small stick of wood twisted around.

   Rack rail (Railroads), a toothed rack, laid as a rail, to afford a hold for teeth on the driving wheel of a locomotive for climbing steep gradients, as in ascending a mountain.

   Rack saw, a saw having wide teeth.

   Rack stick, the stick used in a rack lashing.

   To be on the rack, to suffer torture, physical or mental.

   To live at rack and manger, to live on the best at another's expense. [Colloq.]

   To put to the rack, to subject to torture; to torment.

   A fit of the stone puts a king to the rack, and makes him as miserable as it does the meanest subject.
   --Sir W. Temple.