The Collaborative International Dictionary of English v.0.48:

Lap \Lap\ (l[a^]p), n. [OE. lappe, AS. l[ae]ppa; akin to D. lap
   patch, piece, G. lappen, OHG. lappa, Dan. lap, Sw. lapp.]
   1. The loose part of a coat; the lower part of a garment that
      plays loosely; a skirt; an apron. --Chaucer.
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   2. An edge; a border; a hem, as of cloth. --Chaucer.
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            If he cuts off but a lap of truth's garment, his
            heart smites him.                     --Fuller.
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   3. The part of the clothing that lies on the knees or thighs
      when one sits down; that part of the person thus covered;
      figuratively, a place of rearing and fostering; as, to be
      reared in the lap of luxury.
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            Men expect that happiness should drop into their
            laps.                                 --Tillotson.
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   4. That part of any substance or fixture which extends over,
      or lies upon, or by the side of, a part of another; as,
      the lap of a board; also, the measure of such extension
      over or upon another thing.
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   Note: The lap of shingles or slates in roofing is the
         distance one course extends over the second course
         below, the distance over the course immediately below
         being called the cover.
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   5. (Steam Engine) The amount by which a slide valve at its
      half stroke overlaps a port in the seat, being equal to
      the distance the valve must move from its mid stroke
      position in order to begin to open the port. Used alone,
      lap refers to outside lap. See Outside lap (below).
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   6. The state or condition of being in part extended over or
      by the side of something else; or the extent of the
      overlapping; as, the second boat got a lap of half its
      length on the leader.
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   7. One circuit around a race track, esp. when the distance is
      a small fraction of a mile; as, to run twenty laps; to win
      by three laps. See Lap, to fold, 2.
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   8. In card playing and other games, the points won in excess
      of the number necessary to complete a game; -- so called
      when they are counted in the score of the following game.
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   9. (Cotton Manuf.) A sheet, layer, or bat, of cotton fiber
      prepared for the carding machine.
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   10. (Mach.) A piece of brass, lead, or other soft metal, used
       to hold a cutting or polishing powder in cutting glass,
       gems, and the like, or in polishing cutlery, etc. It is
       usually in the form of wheel or disk, which revolves on a
       vertical axis.
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   Lap joint, a joint made by one layer, part, or piece,
      overlapping another, as in the scarfing of timbers.

   Lap weld, a lap joint made by welding together overlapping
      edges or ends.

   Inside lap (Steam Engine), lap of the valve with respect to
      the exhaust port.

   Outside lap, lap with respect to the admission, or steam,
      port.
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WordNet (r) 3.0 (2006):

lap joint
    n 1: joint made by overlapping two ends and joining them
         together [syn: lap joint, splice]