The Collaborative International Dictionary of English v.0.48:

Impose \Im*pose"\, v. t. [imp. & p. p. Imposed; p. pr. & vb.
   n. Imposing.] [F. imposer; pref. im- in + poser to place.
   See Pose, v. t.]
   1. To lay on; to set or place; to put; to deposit.
      [1913 Webster]

            Cakes of salt and barley [she] did impose
            Within a wicker basket.               --Chapman.
      [1913 Webster]

   2. To lay as a charge, burden, tax, duty, obligation,
      command, penalty, etc.; to enjoin; to levy; to inflict;
      as, to impose a toll or tribute.
      [1913 Webster]

            What fates impose, that men must needs abide.
                                                  --Shak.
      [1913 Webster]

            Death is the penalty imposed.         --Milton.
      [1913 Webster]

            Thou on the deep imposest nobler laws. --Waller.
      [1913 Webster]

   3. (Eccl.) To lay on, as the hands, in the religious rites of
      confirmation and ordination.
      [1913 Webster]

   4. (Print.) To arrange in proper order on a table of stone or
      metal and lock up in a chase for printing; -- said of
      columns or pages of type, forms, etc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Imposing \Im*pos"ing\, a.
   1. Laying as a duty; enjoining.
      [1913 Webster]

   2. Adapted to impress forcibly; impressive; commanding; as,
      an imposing air; an imposing spectacle. "Large and
      imposing edifices." --Bp. Hobart.
      [1913 Webster]

   3. Deceiving; deluding; misleading.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Imposing \Im*pos"ing\, n. (Print.)
   The act of imposing the columns of a page, or the pages of a
   sheet. See Impose, v. t., 4.
   [1913 Webster]

   Imposing stone (Print.), the stone on which the pages or
      columns of types are imposed or made into forms; -- called
      also imposing table.
      [1913 Webster]

WordNet (r) 3.0 (2006):

imposing
    adj 1: impressive in appearance; "a baronial mansion"; "an
           imposing residence"; "a noble tree"; "severe-looking
           policemen sat astride noble horses"; "stately columns"
           [syn: baronial, imposing, noble, stately]
    2: used of a person's appearance or behavior; befitting an
       eminent person; "his distinguished bearing"; "the monarch's
       imposing presence"; "she reigned in magisterial beauty" [syn:
       distinguished, grand, imposing, magisterial]

Moby Thesaurus II by Grady Ward, 1.0:

120 Moby Thesaurus words for "imposing":
   Babylonian, Corinthian, adipose, aristocratic, arty, august,
   awe-inspiring, awful, barbaric, baronial, beefy, big, big-bellied,
   bloated, blowzy, bosomy, brawny, burly, buxom, chubby, chunky,
   commanding, corpulent, courtly, deluxe, dignified, distended,
   dumpy, earnest, effective, elaborate, elegant, extravagant, fancy,
   fat, fatal, fateful, fattish, fine, fleshy, formidable, full,
   glorious, grand, grandiose, grave, gross, heavy, heavyset, hefty,
   high, hippy, imperial, impressive, kingly, lordly, lusty,
   luxurious, magisterial, magnificent, majestic, meaty, moving,
   noble, obese, overblown, overweight, palatial, paunchy, plump,
   plush, podgy, portentous, portly, posh, potbellied, princely,
   proud, pudgy, puffy, pursy, queenly, regal, ritzy, roly-poly,
   rotund, royal, sedate, serious, sober, solemn, sounding,
   splendacious, splendid, splendiferous, square, squat, squatty,
   stalwart, stately, statuesque, stocky, stout, strapping, sumptuous,
   superb, superfancy, superfine, swank, swanky, swell, swollen,
   thick-bodied, thickset, top-heavy, tubby, venerable, weighty,
   well-fed, worthy