The Collaborative International Dictionary of English v.0.48:

Entrain \En*train"\, v. t. [F. entrainer.]
   To draw along as a current does; as, water entrained by
   steam.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Entrain \En*train"\, v. t. [Pref. en- + train.]
   To put aboard a railway train; as, to entrain a regiment.
   [Recent, Eng.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Entrain \En*train"\, v. i.
   To go aboard a railway train; as, the troops entrained at the
   station. [Recent, Eng.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

entrain
    v 1: board a train

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "entrain":
   bicycle, bike, board, bus, catch a train, chauffeur, cycle, drive,
   embark, embus, emplane, enplane, go aboard, go by rail,
   go on board, go on shipboard, joyride, make a train, motor,
   motorcycle, pedal, put to sea, ride, take a joyride, take ship,
   taxi, weigh anchor, wheel