WordNet (r) 3.0 (2006):

step down
    v 1: give up or retire from a position; "The Secretary of the
         Navy will leave office next month"; "The chairman resigned
         over the financial scandal" [syn: leave office, quit,
         step down, resign] [ant: take office]
    2: reduce the level or intensity or size or scope of; "de-
       escalate a crisis" [syn: de-escalate, weaken, step
       down] [ant: escalate, intensify, step up]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "step down":
   abridge, amplify, charge, compress, curtail, cut, cut back,
   cut down, damp, dampen, decrease, deduct, deflate, depreciate,
   depress, diminish, downgrade, electrify, energize, galvanize,
   generate, lessen, loop in, lower, pare, plug in, reduce, retrench,
   roll back, scale down, shock, short, short-circuit, shorten,
   simplify, step up, stiffen, switch off, switch on, take from,
   tune down, turn off, turn on