Dictionary:

Algonquian

  (ăl-gŏng'kwē-ən, -kē-ən) also Algonkian (-kē-ən)

1. A family of North American Indian languages spoken or formerly spoken in an area from Labrador to the Carolinas between the Atlantic coast and the Rocky Mountains.
2. A member of a people traditionally speaking an Algonquian language.

[From ALGONQUIN.]

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: Algonquin

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

The adjective Algonquian has one meaning:

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