WordNet sense 1 (a relation of direct opposition):

contrary, opposite, contrary

WordNet sense 2 (an unfortunate happening that hinders or impedes; something that is thwarting or frustrating):

blow, reversal, setback, black eye

WordNet sense 3 (the side of a coin or medal that does not bear the principal design):

verso

WordNet sense 4 (annul by recalling or rescinding):

annul, countermand, lift, overturn, repeal, rescind, revoke, vacate

WordNet sense 5 (rule against):

override, overrule, overthrow

WordNet sense 6 (turn inside out or upside down):

invert, turn back

WordNet sense 7 (turning in the opposite direction):

reversion, turnabout, turnaround

WordNet sense 8 (directed or moving toward the rear):

rearward

WordNet sense 9 (reversed (turned backward) in order or nature or effect):

inverse

WordNet sense 10 (change to the contrary):

turn, change by reversal