WordNet (r) 3.0 (2006):

mark off
    v 1: set boundaries to and delimit; "mark out the territory"
         [syn: mark off, mark out]
    2: put a check mark on or near or next to; "Please check each
       name on the list"; "tick off the items"; "mark off the units"
       [syn: check, check off, mark, mark off, tick off,
       tick]

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "mark off":
   allocate, allot, analyze, anatomize, appoint, appropriate to,
   assign, assign to, atomize, be characteristic, blaze,
   blaze a trail, blemish, blotch, blueprint, bound, brand, chalk,
   chalk up, change, characterize, chart, check, check off,
   chop logic, cicatrize, circle in, circumscribe, dapple, dash,
   define, delimit, delimitate, demarcate, describe, destine,
   desynonymize, detail, determine, diagram, difference,
   differentiate, discolor, discriminate, disequalize, disjoin,
   distinguish, diversify, divide, dot, earmark, enclose, engrave,
   fate, fix, fleck, freckle, gash, graph, hatch, impress, imprint,
   individualize, individuate, keynote, lay off, lay out, line, lot,
   make a distinction, make a mark, make assignments, map, map out,
   mark, mark boundaries, mark out, mark out for, mark the periphery,
   measure off, measure out, modify, mottle, nick, notch, ordain,
   pace off, particularize, pencil, pepper, personalize, plot,
   plot out, point, portion off, prick, print, punch, punctuate,
   puncture, refine a distinction, reserve, restrict, restrict to,
   riddle, rope off, rule off, scar, scarify, schedule, score, scotch,
   scratch, seal, seam, segregate, separate, set, set apart,
   set aside, set off, set out, set the limit, set the pace,
   set the tone, sever, severalize, sketch, sketch out,
   sound the keynote, specialize, specify, speck, speckle,
   split hairs, splotch, spot, stain, stake out, stamp, step off,
   stigmatize, streak, striate, stripe, surround, tag, tattoo, tick,
   tick off, trace, underline, underscore, vary