WordWeb Online

1. Not meant or adapted for a particular purpose
   "a solvent unsuitable for use on wood surfaces"
    
2. Not capable of being applied
   - inapplicable
    
3. Not conducive to good moral development
   "the movie is unsuitable for children"
    
4. Not worthy of being chosen (especially as a spouse)
   - undesirable

See also: bad, beside the point, ineligible, irrelevant, unfit, unsuitableness