The Collaborative International Dictionary of English v.0.48:

Use \Use\, n. [OE. us use, usage, L. usus, from uti, p. p. usus,
   to use. See Use, v. t.]
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   1. The act of employing anything, or of applying it to one's
      service; the state of being so employed or applied;
      application; employment; conversion to some purpose; as,
      the use of a pen in writing; his machines are in general
      use.
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            Books can never teach the use of books. --Bacon.
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            This Davy serves you for good uses.   --Shak.
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            When he framed
            All things to man's delightful use.   --Milton.
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   2. Occasion or need to employ; necessity; as, to have no
      further use for a book. --Shak.
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   3. Yielding of service; advantage derived; capability of
      being used; usefulness; utility.
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            God made two great lights, great for their use
            To man.                               --Milton.
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            'T is use alone that sanctifies expense. --Pope.
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   4. Continued or repeated practice; customary employment;
      usage; custom; manner; habit.
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            Let later age that noble use envy.    --Spenser.
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            How weary, stale, flat and unprofitable,
            Seem to me all the uses of this world! --Shak.
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   5. Common occurrence; ordinary experience. [R.]
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            O Caesar! these things are beyond all use. --Shak.
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   6. (Eccl.) The special form of ritual adopted for use in any
      diocese; as, the Sarum, or Canterbury, use; the Hereford
      use; the York use; the Roman use; etc.
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            From henceforth all the whole realm shall have but
            one use.                              --Pref. to
                                                  Book of Common
                                                  Prayer.
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   7. The premium paid for the possession and employment of
      borrowed money; interest; usury. [Obs.]
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            Thou art more obliged to pay duty and tribute, use
            and principal, to him.                --Jer. Taylor.
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   8. [In this sense probably a corruption of OF. oes, fr. L.
      opus need, business, employment, work. Cf. Operate.]
      (Law) The benefit or profit of lands and tenements. Use
      imports a trust and confidence reposed in a man for the
      holding of lands. He to whose use or benefit the trust is
      intended shall enjoy the profits. An estate is granted and
      limited to A for the use of B.
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   9. (Forging) A stab of iron welded to the side of a forging,
      as a shaft, near the end, and afterward drawn down, by
      hammering, so as to lengthen the forging.
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   Contingent use, or Springing use (Law), a use to come
      into operation on a future uncertain event.

   In use.
      (a) In employment; in customary practice observance.
      (b) In heat; -- said especially of mares. --J. H. Walsh.

   Of no use, useless; of no advantage.

   Of use, useful; of advantage; profitable.

   Out of use, not in employment.

   Resulting use (Law), a use, which, being limited by the
      deed, expires or can not vest, and results or returns to
      him who raised it, after such expiration.

   Secondary use, or Shifting use, a use which, though
      executed, may change from one to another by circumstances.
      --Blackstone.

   Statute of uses (Eng. Law), the stat. 27 Henry VIII., cap.
      10, which transfers uses into possession, or which unites
      the use and possession.

   To make use of, To put to use, to employ; to derive
      service from; to use.
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WordNet (r) 3.0 (2006):

in use
    adj 1: (of facilities such as telephones or lavatories)
           unavailable for use by anyone else or indicating
           unavailability; (`engaged' is a British term for a busy
           telephone line); "her line is busy"; "receptionists'
           telephones are always engaged"; "the lavatory is in use";
           "kept getting a busy signal" [syn: busy, engaged, in
           use(p)]
    2: currently being used; "robots are in use throughout industry"