Meaning of “train” - Learner’s Dictionary

train

noun uk us /treɪn/

A1 [ C ] a long, thin vehicle that travels along metal tracks and carries people or goods:

a train journey
We could go by train.
You'll have to catch/get the next train.
train of thought/events

a series of connected thoughts, ideas, or events that come or happen one after the other:

I was interrupted and lost my train of thought.

(Definition of “train noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)