资料来源 : Webster's Revised Unabridged Dictionary (1913)

Idle \I"dle\, a. [Compar. {Idler}; superl. {Idlest}.] [OE. idel,
   AS. [=i]del vain, empty, useless; akin to OS. [=i]dal, D.
   ijdel, OHG. [=i]tal vain, empty, mere, G. eitel, Dan. & Sw.
   idel mere, pure, and prob. to Gr. ? clear, pure, ? to burn.
   Cf. {Ether}.]
   1. Of no account; useless; vain; trifling; unprofitable;
      thoughtless; silly; barren. ``Deserts idle.'' --Shak.

            Every idle word that men shall speak, they shall
            give account thereof in the day of judgment. --Matt.
                                                  xii. 36.

            Down their idle weapons dropped.      --Milton.

            This idle story became important.     --Macaulay.

   2. Not called into active service; not turned to appropriate
      use; unemployed; as, idle hours.

            The idle spear and shield were high uphing.
                                                  --Milton.

   3. Not employed; unoccupied with business; inactive; doing
      nothing; as, idle workmen.

            Why stand ye here all the day idle?   --Matt. xx. 6.

   4. Given rest and ease; averse to labor or employment; lazy;
      slothful; as, an idle fellow.

   5. Light-headed; foolish. [Obs.] --Ford.

   {Idle pulley} (Mach.), a pulley that rests upon a belt to
      tighten it; a pulley that only guides a belt and is not
      used to transmit power.

   {Idle wheel} (Mach.), a gear wheel placed between two others,
      to transfer motion from one to the other without changing
      the direction of revolution.

   {In idle}, in vain. [Obs.] ``God saith, thou shalt not take
      the name of thy Lord God in idle.'' --Chaucer.

   Syn: Unoccupied; unemployed; vacant; inactive; indolent;
        sluggish; slothful; useless; ineffectual; futile;
        frivolous; vain; trifling; unprofitable; unimportant.

   Usage: {Idle}, {Indolent}, {Lazy}. A propensity to inaction
          is expressed by each of these words; they differ in
          the cause and degree of this characteristic. Indolent
          denotes an habitual love to ease, a settled dislike of
          movement or effort; idle is opposed to {busy}, and
          denotes a dislike of continuous exertion. Lazy is a
          stronger and more contemptuous term than indolent.

资料来源 : WordNet®

idle wheel
     n : a pulley on a shaft that presses against a guide belt to
         guide or tighten it [syn: {idle pulley}, {idler pulley}]