Dictionary:

Algonquin

  (ăl-gŏng'kwĭn, -kĭn) also Algonkin (-kĭn)

1. 1. Any of various Native American peoples inhabiting the Ottawa River valley of Quebec and Ontario.
   2. A member of one of these peoples.
2. Any of the varieties of the Ojibwa language spoken by the peoples called Algonquin.

[Canadian French, from Malecite elakómkwik, they are our relatives.]

The noun has 2 meanings:

Meaning #1: a member of any of the North American Indian groups speaking an Algonquian language and originally living in the subarctic regions of eastern Canada; many Algonquian tribes migrated south into the woodlands from the Mississippi River to the Atlantic coast
  Synonym: Algonquian

Meaning #2: family of North American Indian languages spoken from Labrador to South Carolina and west to the Great Plains
  Synonyms: Algonquian, Algonquian language

The adjective Algonquin has one meaning:

Meaning #1: of or relating to an Algonquian tribe or its people or language
  Synonyms: Algonquian, Algonkian
  Pertains to noun: Algonquian (meaning #1)