The Collaborative International Dictionary of English v.0.48:
Step-down \Step"-down`\, a. (Elec.) Transforming or converting a current of high potential or voltage into one of low voltage; as, a step-down transformer. [Webster 1913 Suppl.]WordNet (r) 3.0 (2006):
step-down n 1: the act of decreasing or reducing something [syn: decrease, diminution, reduction, step-down] [ant: increase, step-up]