[syn: hostile, uncongenial, unfriendly]
3.  used of plant stock or scions;  incapable of being grafted; 
The Collaborative International Dictionary of English v.0.48:
Uncongenial \Uncongenial\
   See congenial.
WordNet (r) 3.0 (2006):
uncongenial
    adj 1: not suitable to your tastes or needs; "the uncongenial
           roommates were always fighting"; "the task was
           uncongenial to one sensitive to rebuffs" [syn:
           uncongenial, incompatible] [ant: congenial]
    2: very unfavorable to life or growth; "a hostile climate"; "an
       uncongenial atmosphere"; "an uncongenial soil"; "the
       unfriendly environment at high altitudes" [syn: hostile,
       uncongenial, unfriendly]
    3: used of plant stock or scions; incapable of being grafted
Moby Thesaurus II by Grady Ward, 1.0:
110 Moby Thesaurus words for "uncongenial":
   Olympian, abhorrent, aloof, antagonistic, antipathetic,
   at cross-purposes, at loggerheads, at odds, at variance, at war,
   autistic, backward, bashful, blank, chilled, chilly, clashing,
   close, cold, constrained, contradictory, contrary, cool, cranky,
   cross, detached, differing, disaccordant, disagreeable,
   disagreeing, discordant, discreet, discrepant, disharmonious,
   dislikable, displeasing, disproportionate, dissident, dissociable,
   dissonant, distant, distasteful, divergent, expressionless,
   forbidding, frigid, frosty, grating, guarded, hostile, icy,
   immiscible, impassive, impersonal, inaccessible, inaccordant,
   incompatible, inharmonious, insociable, intolerable, introverted,
   jangling, jarring, mislikable, modest, mopey, mopish, morose,
   negative, nongregarious, odious, offish, out of accord,
   out of whack, remote, removed, repressed, repugnant, reserved,
   restrained, reticent, retiring, self-contained, self-sufficient,
   shrinking, snug, socially incompatible, standoff, standoffish,
   subdued, sullen, suppressed, unaffable, unapproachable,
   unclubbable, uncommunicative, uncompanionable, undemonstrative,
   unexpansive, unfriendly, ungenial, unharmonious, uninviting,
   unlikable, unlovable, unpleasant, unsociable, unsocial, variant,
   withdrawn