The Collaborative International Dictionary of English v.0.48:

Difficult \Dif"fi*cult\, a. [From Difficulty.]
   1. Hard to do or to make; beset with difficulty; attended
      with labor, trouble, or pains; not easy; arduous.
      [1913 Webster]

   Note: Difficult implies the notion that considerable mental
         effort or skill is required, or that obstacles are to
         be overcome which call for sagacity and skill in the
         agent; as, a difficult task; hard work is not always
         difficult work; a difficult operation in surgery; a
         difficult passage in an author.
         [1913 Webster]

               There is not the strength or courage left me to
               venture into the wide, strange, and difficult
               world, alone.                      --Hawthorne.
         [1913 Webster]

   2. Hard to manage or to please; not easily wrought upon;
      austere; stubborn; as, a difficult person.

   Syn: Arduous; painful; crabbed; perplexed; laborious;
        unaccommodating; troublesome. See Arduous.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Difficult \Dif"fi*cult\, v. t.
   To render difficult; to impede; to perplex. [R.] --Sir W.
   Temple.
   [1913 Webster]

WordNet (r) 3.0 (2006):

difficult
    adj 1: not easy; requiring great physical or mental effort to
           accomplish or comprehend or endure; "a difficult task";
           "nesting places on the cliffs are difficult of access";
           "difficult times"; "why is it so hard for you to keep a
           secret?" [syn: difficult, hard] [ant: easy]
    2: hard to control; "a difficult child", "an unmanageable
       situation" [syn: unmanageable, difficult] [ant:
       manageable]