[1] : 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.
   1913 webster

         and jacob said . . . with my staff i passed over this
         jordan, and now i am become two bands.   --gen. xxxii.
                                                  9, 10.
   1913 webster

         thy name shall be called no more jacob, but israel.
                                                  --gen. xxxii.
                                                  28.
   1913 webster

   jacob's ladder.
   a bot. a perennial herb of the genus polemonium
       polemonium coeruleum, 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.
       1913 webster
see also:
jack israel jacob's ladder polemonium polemonium coeruleum, having corymbs of drooping flowers, usually blue. gray jacob's membrane 
retina jacob's staff staff 

[2] : WordNet (r) 2.0

jacob's ladder
     n 1: pinnate-leaved european perennial having bright blue or
          white flowers syn: greek valerian, charity, polemonium
          caeruleum, polemonium van-bruntiae, polymonium
          caeruleum van-bruntiae
     2: nautical a hanging ladder of ropes or chains supporting
        wooden or metal rungs or steps syn: jack ladder, pilot
        ladder
see also:
greek valerian charity polemonium caeruleum polemonium van-bruntiae polymonium caeruleum van-bruntiae jack ladder 
pilot ladder 

Jacobs Ladder >> J Words
Jacobs Ladder, definition of term: Jacobs Ladder
jacobs+ladder_pag1.html

Ladder >> L Words
Ladder, definition of term: Ladder
ladder_pag1.html

Fish Ladder >> F Words
Fish Ladder, definition of term: Fish Ladder
fish+ladder_pag1.html