IPA: /ˈtreɪnˌfʊl/
KK: /trɛnˌfəl/
A large amount or quantity of something, often used to describe the load or capacity of a train.
The trainful of goods arrived at the station early in the morning.
The word 'trainful' is formed from 'train' (from Old French *traïner*, meaning to drag or pull) and '-ful' (meaning full of). The word 'trainful' means full of trains or having the capacity of a train.
Think of something that is 'full of' ('-ful') the action of 'dragging' or 'pulling' ('train') — that's why 'trainful' refers to something that has the capacity of a train.