WordWeb Online

1. Not suitable to your tastes or needs
   "the uncongenial roommates were always fighting"; "the task was uncongenial to one sensitive to rebuffs"
   - incompatible
    
2. Very unfavourable to life or growth
   "an uncongenial atmosphere"; "an uncongenial soil"
   - hostile, unfriendly
    
3. Used of plant stock or scions; incapable of being grafted

See also: disagreeable, incompatible, inhospitable, uncongeniality, unfriendly, unsympathetic

Antonym: congenial