What is "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[=i]pan (in comp.), akin to G. schleifen to slide, glide, drag, whet, OHG. sl[=i]fan to slide, glide, make smooth, Icel. sl[=i]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.

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.

3. To move or fly (out of place); to shoot; -- often with out, off, etc.; as, a bone may slip out of its place.

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.

   Thus one tradesman slips away, To give his partner fairer play.
   --Prior.

   Thrice the flitting shadow slipped away.
   --Dryden.

5. To err; to fall into error or fault.

   There is one that slippeth in his speech, but not from his heart.
   --Ecclus. xix. 1

6. To let slip, to loose from the slip or noose, as a hound; to allow to escape.

   Cry, ``Havoc,'' and let slip the dogs of war.
   --Shak.