The Collaborative International Dictionary of English v.0.48:

Trainband \Train"band`\, n.; pl. Trainbands.
   A band or company of an organized military force instituted
   by James I. and dissolved by Charles II.; -- afterwards
   applied to the London militia. [Eng.]
   [1913 Webster]

         He felt that, without some better protection than that
         of the trainbands and Beefeaters, his palace and person
         would hardly be secure.                  --Macaulay.
   [1913 Webster]

         A trainband captain eke was he
         Of famous London town.                   --Cowper.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trainband
    n 1: a company of militia in England or America from the 16th
         century to the 18th century