The Collaborative International Dictionary of English v.0.48:

Jacob \Ja"cob\, n. [Cf. F. Jacob. See 2d Jack.]
   A Hebrew patriarch (son of Isaac, and ancestor of the Jews),
   who in a vision saw a ladder reaching up to heaven (--Gen.
   xxviii. 12); -- also called Israel.
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         And Jacob said . . . with my staff I passed over this
         Jordan, and now I am become two bands.   --Gen. xxxii.
                                                  9, 10.
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         Thy name shall be called no more Jacob, but Israel.
                                                  --Gen. xxxii.
                                                  28.
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   Jacob's ladder.
   (a) (Bot.) A perennial herb of the genus Polemonium
       (Polemonium c[oe]ruleum), having corymbs of drooping
       flowers, usually blue. Gray.
   (b) (Naut.) A rope ladder, with wooden steps, for going
       aloft. --R. H. Dana, Jr.
   (c) (Naut.) A succession of short cracks in a defective spar.


   Jacob's membrane. See Retina.

   Jacob's staff.
   (a) A name given to many forms of staff or weapon, especially
       in the Middle Ages; a pilgrim's staff. [Obs.] --Spenser.
   (b) (Surveying) See under Staff.
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