The Collaborative International Dictionary of English v.0.48:

Ethos \E"thos\, n. [L., fr. Gr. ? character. See Ethic.]
   1. The character, sentiment, or disposition of a community or
      people, considered as a natural endowment; the spirit
      which actuates manners and customs; also, the
      characteristic tone or genius of an institution or social
      organization.
      [Webster 1913 Suppl.]

   2. (esthetics) The traits in a work of art which express the
      ideal or typic character -- character as influenced by the
      ethos (sense 1) of a people -- rather than realistic or
      emotional situations or individual character in a narrow
      sense; -- opposed to pathos.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

ethos
    n 1: (anthropology) the distinctive spirit of a culture or an
         era; "the Greek ethos"

Moby Thesaurus II by Grady Ward, 1.0:

145 Moby Thesaurus words for "ethos":
   Ten Commandments, Weltanschauung, Zeitgeist, acculturation,
   assumption, attitude, axiology, behavioral norm, body of ideas,
   body-build, brand, business ethics, cast, character,
   characteristic, characteristics, civilization, climate,
   climate of opinion, code, code of ethics, code of morals,
   common belief, community sentiment, complex, complexion,
   composition, conceit, concept, conception, conclusion,
   consensus gentium, consideration, constituents, constitution,
   crasis, cultural drift, culture, culture area, culture center,
   culture complex, culture conflict, culture contact,
   culture pattern, culture trait, decalogue, dharma, diathesis,
   disposition, estimate, estimation, ethic, ethical system, ethics,
   eye, feeling, fiber, folkways, frame, general belief, genius,
   grain, habit, hue, humor, humors, idea, ideology, ilk, impression,
   intellectual climate, judgment, key trait, kind, legal ethics,
   lights, makeup, medical ethics, mind, mold, moral climate,
   moral code, moral principles, morals, mores, mystique, nature,
   new morality, norm, normative system, norms, notion, observation,
   opinion, personal judgment, philosophy, physique, point of view,
   popular belief, position, posture, practices, presumption,
   prevailing belief, principles, professional ethics, property,
   public belief, public opinion, quality, reaction, sentiment, sight,
   social ethics, society, somatotype, sort, spirit,
   spiritual climate, stamp, stance, standards, streak, stripe,
   suchness, system, system of ideas, system of theories, temper,
   temperament, tendency, tenor, theory, thinking, thought, tone,
   trait, trait-complex, type, value system, vein, view, way,
   way of thinking, world view