The Collaborative International Dictionary of English v.0.48:

Uphill \Up*hill"\, adv.
   Upwards on, or as on, a hillside; as, to walk uphill.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Uphill \Up"hill`\, a.
   1. Ascending; going up; as, an uphill road.
      [1913 Webster]

   2. Attended with labor; difficult; as, uphill work.
      [1913 Webster]

WordNet (r) 3.0 (2006):

uphill
    adv 1: against difficulties; "she was talking uphill"
    2: upward on a hill or incline; "this street lay uphill"
    adj 1: sloping upward [syn: acclivitous, rising, uphill]
    n 1: the upward slope of a hill

Moby Thesaurus II by Grady Ward, 1.0:

166 Moby Thesaurus words for "uphill":
   Herculean, abruptness, abstruse, acclinate, acclivitous, acclivity,
   anabasis, anabatic, arduous, ascendant, ascending, ascension,
   ascensional, ascensive, ascent, aslant, aslantwise, aslope,
   at a slant, atilt, backbreaking, brutal, burdensome, clamber,
   climb, climbing, complex, critical, crushing, delicate, demanding,
   difficile, difficult, downgrade, downhill, effortful, elevation,
   escalade, exacting, forced, formidable, fountain, grueling, gush,
   gyring up, hairy, hard, hard-earned, hard-fought, heavenward,
   heavy, hefty, in the ascendant, increase, intricate, jawbreaking,
   jet, jump, killing, knotted, knotty, labored, laborious, leap,
   leaping, levitation, mean, mount, mounting, no picnic, not easy,
   off plumb, onerous, operose, oppressive, painful, precipitousness,
   punishing, rakingly, rampant, rearing, rigorous, rise, rising,
   rising ground, rocketing up, rough, rugged, saltation, saltatory,
   scandent, scansorial, set with thorns, severe, shooting up,
   skyrocketing, skyward, slantingly, slantways, slantwise,
   slaunchways, slopeways, slopingly, soaring, spiny, spiraling,
   spout, spring, springing, spurt, steep, steepness, strained,
   strenuous, surge, takeoff, taking off, thorny, ticklish, tipsily,
   toilsome, tough, tricky, troublesome, up, up attic, up north,
   up steps, upalong, uparching, upclimb, upcoming, updraft, upgang,
   upgo, upgoing, upgrade, upgrowth, uphillward, upleap, uplift,
   uplong, upping, uprisal, uprise, uprising, uprush, upshoot,
   upslope, upsloping, upstairs, upstream, upstreamward, upsurge,
   upsurgence, upsweep, upswing, uptown, upward, upwards, upwith,
   vault, verticalness, wearisome, wicked, zooming