WordWeb Online

1. Having self-possession upset; thrown into confusion
   "looked at each other dumbly, quite disconcerted";
   - discombobulated, rattled [informal], thrown

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: discomposed

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