NOUN (2)

1. the feeling caused by disagreeable stimuli; one pole of a continuum of states of feeling;

2. the quality of giving displeasure;
- Example: "the recent unpleasantness of the weather"

The Collaborative International Dictionary of English v.0.48:

Unpleasant \Un*pleas"ant\, a.
   Not pleasant; not amiable or agreeable; displeasing;
   offensive. -- Un*pleas"ant*ly, adv. -- Un*pleas"ant*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unpleasantness
    n 1: the feeling caused by disagreeable stimuli; one pole of a
         continuum of states of feeling [ant: pleasantness]
    2: the quality of giving displeasure; "the recent unpleasantness
       of the weather" [ant: pleasantness, sweetness]