WordWeb Online

1. Causing an emotional disturbance
   "his disconcerting habit of greeting friends ferociously and strangers charmingly";
   - upsetting

1. Cause to feel embarrassment
   "The constant attention of the young man disconcerted her";
   - confuse, flurry, put off
    
2. Cause to lose one's composure
   - upset, discompose, untune, discomfit

See also: displeasing

Type of: abash, arouse, elicit, embarrass, enkindle [literary], evoke, fire, kindle, provoke, raise