The Collaborative International Dictionary of English v.0.48:

Pathos \Pa"thos\ (p[=a]"th[o^]s), n. [L., from Gr. pa`qos a
   suffering, passion, fr. paqei^n, pas`chein, to suffer; cf.
   po`nos toil, L. pati to suffer, E. patient.]
   That quality or property of anything which touches the
   feelings or excites emotions and passions, esp., that which
   awakens tender emotions, such as pity, sorrow, and the like;
   contagious warmth of feeling, action, or expression; pathetic
   quality; as, the pathos of a picture, of a poem, or of a cry.
   [1913 Webster]

         The combination of incident, and the pathos of
         catastrophe.                             --T. Warton.
   [1913 Webster]

   1. The quality or character of those emotions, traits, or
      experiences which are personal, and therefore restricted
      and evanescent; transitory and idiosyncratic dispositions
      or feelings as distinguished from those which are
      universal and deep-seated in character; -- opposed to
      ethos.
      [Webster 1913 Suppl.]

   2. Suffering; the enduring of active stress or affliction.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

pathos
    n 1: a quality that arouses emotions (especially pity or
         sorrow); "the film captured all the pathos of their
         situation" [syn: pathos, poignancy]
    2: a feeling of sympathy and sorrow for the misfortunes of
       others; "the blind are too often objects of pity" [syn:
       commiseration, pity, ruth, pathos]
    3: a style that has the power to evoke feelings

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "pathos":
   bathos, benevolence, bitterness, bleakness, caring, cheerlessness,
   chord, clemency, comfortlessness, commiseration, compassion,
   concern, condolence, depression, discomfort, dismalness, distress,
   distressfulness, dreariness, echo, empathy, favor, feeling,
   fellow feeling, forbearance, forgiveness, grace, grief,
   grievousness, heaviness, heaviness of heart, heavy heart,
   heavyheartedness, humanity, identification, involvement,
   joylessness, kindness, lamentability, lamentation, leniency, mercy,
   mitigation, mournfulness, pain, painfulness, pardon, pitiability,
   pitiableness, pitifulness, pity, poignancy, quarter,
   regrettableness, relating, relief, reprieve, response,
   responsiveness, ruth, sadheartedness, sadness, self-pity, sharing,
   sharpness, sorrowfulness, sympathetic chord, sympathetic response,
   sympathy, vibes, vibrations, woebegoneness, woefulness