Source : Webster's Revised Unabridged Dictionary (1913)

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

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

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

Source : WordNet®

entrain
     v : board a train