To let slip

Slip \Slip\, v. i. [imp. & p. p. {Slipped}; p. pr. & vb. n.
   {Slipping}.] [OE. slippen; akin to LG. & D. slippen, MHG.
   slipfen (cf. Dan. slippe, Sw. slippa, Icel. sleppa), and fr.
   OE. slipen, AS. sl[imac]pan (in comp.), akin to G. schleifen
   to slide, glide, drag, whet, OHG. sl[imac]fan to slide,
   glide, make smooth, Icel. sl[imac]pa to whet; cf. also AS.
   sl?pan, Goth. sliupan, OS. slopian, OHG. sliofan, G.
   schliefen, schl?pfen, which seem to come from a somewhat
   different root form. Cf. {Slope}, n.]
   1. To move along the surface of a thing without bounding,
      rolling, or stepping; to slide; to glide.
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   2. To slide; to lose one's footing or one's hold; not to
      tread firmly; as, it is necessary to walk carefully lest
      the foot should slip.
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   3. To move or fly (out of place); to shoot; -- often with
      out, off, etc.; as, a bone may slip out of its place.
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   4. To depart, withdraw, enter, appear, intrude, or escape as
      if by sliding; to go or come in a quiet, furtive manner;
      as, some errors slipped into the work.
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            Thus one tradesman slips away,
            To give his partner fairer play.      --Prior.
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            Thrice the flitting shadow slipped away. --Dryden.
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   5. To err; to fall into error or fault.
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            There is one that slippeth in his speech, but not
            from his heart.                       --Ecclus. xix.
                                                  16.
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   {To let slip}, to loose from the slip or noose, as a hound;
      to allow to escape.
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            Cry, "Havoc," and let slip the dogs of war. --Shak.
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