1. [adj]  used of plant stock or scions; incapable of being grafted
2. [adj]  not suitable to your tastes or needs; "the uncongenial roommates were always fighting"; "the task was uncongenial to one sensitive to rebuffs"
3. [adj]  very unfavorable to life or growth; "a hostile climate"; "an uncongenial atmosphere"; "an uncongenial soil"; "the unfriendly environment at high altitudes"

UNCONGENIAL is a 11 letter word that starts with U.