WordNet (r) 3.0 (2006):

mark down
    v 1: reduce the price of [ant: mark up]

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "mark down":
   beat down, book, break, calendar, carve, catalog, chalk, chalk up,
   cheapen, check in, chronicle, clip, cut, cut back, cut down,
   cut prices, decline, decry, deflate, depreciate, devaluate,
   devalue, dive, docket, downgrade, engrave, enroll, enscroll, enter,
   fall, fall in price, file, fill out, give way, grave, impanel,
   incise, index, inscribe, insert, jew down, jot down, list, log,
   lower, make a memorandum, make a note, make an entry, make out,
   matriculate, minute, nose-dive, note, note down, pare,
   place upon record, plummet, plunge, poll, post, post up, put down,
   put in writing, put on paper, put on tape, record, reduce,
   reduce to writing, register, sag, set down, shave, slash, slump,
   tabulate, take down, tape, tape-record, trim, underprize,
   undervalue, videotape, write, write down, write in, write off,
   write out, write up