Source : Webster's Revised Unabridged Dictionary (1913)

Thoughtful \Thought"ful\, a.
   1. Full of thought; employed in meditation; contemplative;
      as, a man of thoughtful mind.

            War, horrid war, your thoughtful walks invades.
                                                  --Pope.

   2. Attentive; careful; exercising the judgment; having the
      mind directed to an object; as, thoughtful of gain;
      thoughtful in seeking truth. --Glanvill.

   3. Anxious; solicitous; concerned.

            Around her crowd distrust, and doubt, and fear, And
            thoughtful foresight, and tormenting care. --Prior.

   Syn: Considerate; deliberate; contemplative; attentive;
        careful; wary; circumspect; reflective; discreet.

   Usage: {Thoughtful}, {Considerate}. He who is habitually
          thoughtful rarely neglects his duty or his true
          interest; he who is considerate pauses to reflect and
          guard himself against error. One who is not thoughtful
          by nature, if he can be made considerate, will usually
          be guarded against serious mistakes. ``He who is
          thoughtful does not forget his duty; he who is
          considerate pauses, and considers properly what is his
          duty. It is a recommendation to a subordinate person
          to be thoughtful in doing what is wished of him; it is
          the recommendation of a confidential person to be
          considerate, as he has often to judge according to his
          own discretion. --Crabb. -- {Thought"ful*ly}, adv. --
          {Thought"ful*ness}, n.

Source : WordNet®

thoughtfully
     adv 1: in a thoughtful manner; "he stared thoughtfully out the
            window" [ant: {thoughtlessly}]
     2: showing thoughtfulness; "he had thoughtfully brought with
        him some food" [ant: {thoughtlessly}]