WordWeb Online

1. Favouring one person or side over another
   - biased, colored [US], coloured [Brit, Cdn], slanted
    
2. Not reversible or capable of having either side out
   - nonreversible
    
3. Involving only one part or side
   "one-sided paralysis";
   - unilateral
    
4. Poorly balanced or matched in quantity or value or measure
   - unequal

See also: anisometric, equality, incommensurate, mismatched, nonequivalent, odds-on, one-party, partial, unbalanced, unequalised [Brit], unequalized, uneven, unsymmetrical

Encyclopedia: One-sided