Jacob's ladder Meaning, Definition & Usage

  1. noun pinnate-leaved European perennial having bright blue or white flowers
    Polemonium caeruleum; Greek valerian; Polymonium caeruleum van-bruntiae; Polemonium van-bruntiae; charity.
  2. noun (nautical) a hanging ladder of ropes or chains supporting wooden or metal rungs or steps
    jack ladder; pilot ladder.

WordNet

Definitions
  1. . (a) (Bot.) A perennial herb of the genus Polemonium (P. 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.

Webster 1913