Merriam-Webster Collegiate Dictionary - entrain

 I. transitive verb  Etymology: Middle French ~er, from en- + trainer to draw, drag — more at train  Date: 1568  1. to draw along with or after oneself  2. to draw in and transport (as solid particles or gas) by the flow of a fluid  3. to incorporate (air bubbles) into concrete  4. to determine or modify the phase or period of circadian rhythms ~ed by a light cycle  • ~er noun  • ~ment noun  II. verb  Date: 1881  transitive verb to put aboard a train  intransitive verb to go aboard a train