From Longman Dictionary of Contemporary Englishset something in trainset something in trainBritish English formalSTART something/MAKE something START to make a process start happening Plans to modernize have been set in train. → train
Examples from the Corpus
set something in train• It is easy to make him look personally responsible for setting the process in train and bringing it to fruition.• Why, oh, why did you set such enquiries in train? 