Source : Webster's Revised Unabridged Dictionary (1913)

Pillow \Pil"low\, n. [OE. pilwe, AS. pyle, fr. L. pilvinus.]
   1. Anything used to support the head of a person when
      reposing; especially, a sack or case filled with feathers,
      down, hair, or other soft material.

            [Resty sloth] finds the down pillow hard. --Shak.

   2. (Mach.) A piece of metal or wood, forming a support to
      equalize pressure; a brass; a pillow block. [R.]

   3. (Naut.) A block under the inner end of a bowsprit.

   4. A kind of plain, coarse fustian.

   {Lace pillow}, a cushion used in making hand-wrought lace.

   {Pillow bier} [OE. pilwebere; cf. LG. b["u]re a pillowcase],
      a pillowcase; pillow slip. [Obs.] --Chaucer.

   {Pillow block} (Mach.), a block, or standard, for supporting
      a journal, as of a shaft. It is usually bolted to the
      frame or foundation of a machine, and is often furnished
      with journal boxes, and a movable cover, or cap, for
      tightening the bearings by means of bolts; -- called also
      {pillar block}, or {plumber block}.

   {Pillow lace}, handmade lace wrought with bobbins upon a lace
      pillow.

   {Pillow of a plow}, a crosspiece of wood which serves to
      raise or lower the beam.

   {Pillow sham}, an ornamental covering laid over a pillow when
      not in use.

   {Pillow slip}, a pillowcase.

Source : WordNet®

pillow slip
     n : bed linen consisting of a cover for a pillow; "the burglar
         carried his loot in a pillowcase" [syn: {case}, {pillowcase},
          {slip}]