The Collaborative International Dictionary of English v.0.48:

Mayan \Ma"yan\ (m[aum]"yan), a.
   1. Designating, or pertaining to, an American Indian
      linguistic stock occupying the Mexican States of Veracruz,
      Chiapas, Tabasco, Campeche, and Yucatan, together with a
      part of Guatemala and a part of El Salvador. See 2nd
      Maya.
      [Webster 1913 Suppl.]

   2. Of or pertaining to the Mayas.
      [Webster 1913 Suppl.] Mayan arch

WordNet (r) 3.0 (2006):

Mayan
    n 1: a member of an American Indian people of Yucatan and Belize
         and Guatemala who had a culture (which reached its peak
         between AD 300 and 900) characterized by outstanding
         architecture and pottery and astronomy; "Mayans had a
         system of writing and an accurate calendar" [syn: Mayan,
         Maya]
    2: a family of American Indian languages spoken by Maya [syn:
       Maya, Mayan, Mayan language]