WordWeb Online

1. Showing reason or sound judgment
   "a reasonable choice";
   - sensible
    
2. Not excessive or extreme
   "reasonable prices";
   - fair, fairish
    
3. Marked by sound judgment; having good reason
   "reasonable nuclear policy";
   - sane

See also: commonsense, commonsensible, commonsensical, fair, healthy, intelligent, just, levelheaded, level-headed, logical, mod [informal], moderate, rational, reasonableness, sound, tenable, valid, well-founded

Antonym: unreasonable

Encyclopedia: Reasonable, substantial, and probative evidence