The Collaborative International Dictionary of English v.0.48:

Iroquoian \Ir`o*quoi"an\ ([i^]r`[-o]*kwoi"an), a.
   Of, pertaining to, or designating, one of the principal
   linguistic stocks of the North American Indians. The
   territory of the northern Iroquoian tribes, of whom the Five
   Nations, or Iroquois proper, were the chief, extended from
   the shores of the St. Lawrence and of Lakes Huron, Ontario,
   and Erie south, through eastern Pennsylvania, to Maryland;
   that of the southern tribes, of whom the Cherokees were
   chief, formed part of Virginia, the Carolinas, Georgia,
   Tennessee, and Kentucky. All of the tribes were agricultural,
   and they were noted for large, communal houses, palisaded
   towns, and ability to organize, as well as for skill in war.
   -- n. An Indian of an Iroquoian tribe.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Iroquoian
    n 1: a family of North American Indian languages spoken by the
         Iroquois [syn: Iroquoian, Iroquois, Iroquoian
         language]