Source : Webster's Revised Unabridged Dictionary (1913)

Pensive \Pen"sive\, a. [F. pensif, fr. penser to think, fr. L.
   pensare to weigh, ponder, consider, v. intens. fr. pendere to
   weigh. See {Pension}, {Poise}.]
   1. Thoughtful, sober, or sad; employed in serious reflection;
      given to, or favorable to, earnest or melancholy musing.

            The pensive secrecy of desert cell.   --Milton.

            Anxious cares the pensive nymph oppressed. --Pope.

   2. Expressing or suggesting thoughtfulness with sadness; as,
      pensive numbers. --Prior.

Source : WordNet®

pensive
     adj 1: persistently or morbidly thoughtful [syn: {brooding}, {broody},
             {contemplative}, {meditative}, {musing}, {pondering},
             {reflective}, {ruminative}]
     2: showing pensive sadness; "the sensitive and wistful response
        of a poet to the gentler phases of beauty" [syn: {wistful}]