thiamin thia·min US/ˈθaɪʌmʌn/ uncommon noun 1. a B vitamin that prevents beriberi; maintains appetite and growth Synonymsvitamin B1thiamineaneurinantiberiberi factor Related words Word family thiaminethiamine pyrophosphate Broader terms B-complex vitamin WordNet 2.1 (Princeton University). CMU Pronouncing Dictionary. WordNet 2.1 Copyright Princeton University. All rights reserved.