The Collaborative International Dictionary of English v.0.48:

jackboot \jackboot\ n.
   1. a man's high tasseled boot. [19th century]

   Syn: Hessian boot, hessian, Wellington, Wellington boot.
        [WordNet 1.5]

   2. A strong leather boot reaching up to or over the knee; it
      is worn mostly by soldiers.
      [PJC]

WordNet (r) 3.0 (2006):

jackboot
    n 1: (19th century) a man's high tasseled boot [syn: Hessian
         boot, hessian, jackboot, Wellington, Wellington
         boot]