The Collaborative International Dictionary of English v.0.48:

Powwow \Pow"wow`\, n.
   1. A priest, or conjurer, among the North American Indians.
      [1913 Webster]

            Be it sagamore, sachem, or powwow.    --Longfellow.
      [1913 Webster]

   2. Conjuration attended with great noise and confusion, and
      often with feasting, dancing, etc., performed by Indians
      for the cure of diseases, to procure success in hunting or
      in war, and for other purposes.
      [1913 Webster]

   3. Hence: Any assembly characterized by noise and confusion;
      a noisy frolic or gathering. [Archaic, formerly Colloq. U.
      S.]
      [1913 Webster]

   4. Any meeting assembled to discuss an issue; a parley.
      [Informal]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Powwow \Pow"wow`\, v. i.
   1. To use conjuration, with noise and confusion, for the cure
      of disease, etc., as among the North American Indians.
      [1913 Webster]

   2. Hence: To hold a noisy, disorderly meeting. [Archaic,
      formerly Colloq. U. S.]
      [1913 Webster]

   3. To hold a meeting to discuss an issue. [Informal]
      [PJC]

WordNet (r) 3.0 (2006):

powwow
    n 1: (informal) a quick private conference [syn: huddle,
         powwow]
    2: a council of or with Native Americans
    v 1: hold a powwow, talk, conference or meeting

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "powwow":
   advise, advise with, audience, bargain, bargaining,
   bargaining session, call in, collogue, compare notes, conclave,
   confab, confabulate, confabulation, confer, confer with,
   conference, confrontation, congress, constitutional convention,
   consult, consult with, consultation, convention, council,
   council fire, council of war, counsel, county convention,
   deliberate, discuss, discuss with, discussion,
   exchange observations, exchange of views, exchange views,
   eyeball-to-eyeball encounter, have conversations, high-level talk,
   hold conference, huddle, interchange of views, interview, meeting,
   national convention, negotiate, negotiations, news conference,
   nominating convention, palaver, parley, political convention,
   pourparler, preliminary convention, press conference,
   put heads together, quadrennial circus, reason with, refer to,
   seance, session, sit down together, sit down with, sitting,
   state convention, summit, summit conference, summitry,
   take counsel, take up with, talk over, treat