The DICT Development Group

  falling out
      n 1: a personal or social separation (as between opposing
           factions); "they hoped to avoid a break in relations" [syn:
           rupture, breach, break, severance, rift, falling
           out]

  31 Moby Thesaurus words for "falling out":
     alienation, altercation, beef, bickering, breach,
     breach of friendship, break, cleavage, cleft, controversy,
     disaffection, disfavor, dispute, disruption, disunion, disunity,
     divergence, dividedness, division, estrangement, feud, hassle,
     open rupture, recall of ambassadors, rift, row, run-in, rupture,
     schism, separation, split