WordNet (r) 3.0 (2006):

shore up
    v 1: support by placing against something solid or rigid; "shore
         and buttress an old building" [syn: prop up, prop,
         shore up, shore]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "shore up":
   afford support, back, back up, bear, bear out, bear up, beef up,
   bolster, bolster up, brace, brace up, buoy up, buttress, carry,
   case harden, confirm, cradle, crutch, cushion, finance, fortify,
   fund, gird, give support, harden, hold, hold up, invigorate, keep,
   keep afloat, keep up, lend support, mainstay, maintain, nerve,
   pillow, prop, prop up, refresh, reinforce, reinvigorate,
   restrengthen, rigidify, screw up, shore, shoulder, stay, steel,
   stiffen, strengthen, subsidize, subvention, subventionize, support,
   sustain, temper, tense, tighten, toughen, trice up, underbrace,
   undergird, underlie, underpin, underset, upbear, uphold, upkeep