The Collaborative International Dictionary of English v.0.48:

Potlatch \Pot"latch`\, n. [Chinook potlatch, pahtlatch, fr.
   Nootka pahchilt, pachalt, a gift.]
   1. Among the Kwakiutl, Chimmesyan, and other Indians of the
      northwestern coast of North America, a ceremonial
      distribution by a man of gifts to his own and neighboring
      tribesmen, often, formerly, to his own impoverishment.
      Feasting, dancing, and public ceremonies accompany it.
      [Webster 1913 Suppl.]

   2. Hence, a feast given to a large number of persons, often
      accompanied by gifts. [Colloq., Northwestern America]
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

potlatch
    n 1: a ceremonial feast held by some Indians of the northwestern
         coast of North America (as in celebrating a marriage or a
         new accession) in which the host gives gifts to tribesmen
         and others to display his superior wealth (sometimes,
         formerly, to his own impoverishment)

U.S. Gazetteer Places (2000):

Potlatch, ID -- U.S. city in Idaho
   Population (2000):    791
   Housing Units (2000): 357
   Land area (2000):     0.335781 sq. miles (0.869670 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.335781 sq. miles (0.869670 sq. km)
   FIPS code:            64900
   Located within:       Idaho (ID), FIPS 16
   Location:             46.922157 N, 116.897646 W
   ZIP Codes (1990):     83855
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Potlatch, ID
    Potlatch