WordNet (r) 3.0 (2006):

buoy up
    v 1: become more cheerful; "after a glass of wine, he lightened
         up a bit" [syn: lighten, lighten up, buoy up]
    2: make more cheerful; "the conversation lightened me up a bit"
       [syn: lighten, lighten up, buoy up] [ant: weigh down,
       weigh on]
    3: keep afloat; "The life vest buoyed him up" [syn: buoy,
       buoy up]

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "buoy up":
   afford support, animate, back, back up, bear, bear up, bolster,
   bolster up, boost, brace, brighten, buoy, buttress, carry, cast up,
   cheer, cradle, crutch, cushion, elevate, encourage, enliven, erect,
   escalate, exhilarate, float, float high, give a lift, give support,
   gladden, hearten, heave, heft, heighten, heist, hike, hoick, hoist,
   hold, hold up, inspire, inspirit, invigorate, jerk up, keep afloat,
   keep up, knock up, lend support, levitate, lift, lift up, liven,
   lob, loft, mainstay, maintain, perk up, pick up, pillow, prop,
   raise, raise up, rear, rear up, reinforce, rejoice,
   rejoice the heart, ride high, rise, set up, shore, shore up,
   shoulder, sky, stay, stick up, subsidize, subvention, support,
   sustain, throw up, underbrace, undergird, underlie, underpin,
   underset, up, upbear, upbuoy, upcast, upheave, uphoist, uphold,
   upkeep, uplift, upraise, uprear, upthrow, vitalize, waft