The Collaborative International Dictionary of English v.0.48:

Esprit \Es`prit"\, n. [F. See Spirit.]
   Spirit.
   [1913 Webster]

   Esprit de corps, a French phrase much used by English
      writers to denote the common spirit pervading the members
      of a body or association of persons. It implies sympathy,
      enthusiasm, devotion, and jealous regard for the honor of
      the body as a whole.
      [1913 Webster]

WordNet (r) 3.0 (2006):

esprit de corps
    n 1: the spirit of a group that makes the members want the group
         to succeed [syn: esprit de corps, morale, team
         spirit]

Moby Thesaurus II by Grady Ward, 1.0:

136 Moby Thesaurus words for "esprit de corps":
   accord, accordance, affinity, agape, agreement, amity,
   bipartisanship, bonds of harmony, boon companionship, brotherhood,
   brotherliness, brotherly love, camaraderie, caritas,
   cement of friendship, charity, chumship, clannishness, clanship,
   cliqueyness, cliquishness, cliquism, coaction, coadjuvancy,
   coadministration, coagency, cochairmanship, codirectorship,
   collaboration, collaborativeness, colleagueship, collectivism,
   collusion, commensalism, common effort, common enterprise,
   communalism, communion, communism, communitarianism, community,
   community of interest, community of interests, companionship,
   compatibility, complicity, comradeship, concert, concord,
   concordance, concurrence, confraternity, congeniality, consortship,
   cooperation, cooperativeness, correspondence, denominationalism,
   devotion, duet, duumvirate, ecumenicalism, ecumenicism, ecumenism,
   empathy, enthusiasm, esprit, ethnocentricity, exclusiveness,
   faction, factionalism, feeling of identity, fellow feeling,
   fellowship, fraternalism, fraternity, freemasonry,
   frictionlessness, good vibes, good vibrations, happy family,
   harmony, identity, joining of forces, joint effort,
   joint operation, kinship, like-mindedness, love, loyalty,
   mass action, morale, mutual assistance, mutualism, mutuality,
   octet, oneness, partiality, partisanism, partisanship,
   party spirit, peace, pooling, pooling of resources,
   pulling together, quartet, quintet, rapport, rapprochement,
   reciprocity, sectarianism, sectionalism, septet, sextet, sharing,
   sisterhood, sisterliness, sodality, solidarity, sorority, spirit,
   symbiosis, sympathy, symphony, synergism, synergy, team spirit,
   teamwork, trio, triumvirate, troika, understanding, union, unison,
   united action, unity