a person, place or item from Mongolia

a member of the Mongolian people, known as the Mongols

the Mongolian culture

the Mongolian language or the Mongolian alphabet

(historical) the race native to East Asia (later also Mongoloid)

Also, the terms "mongoloid" and "mongolism" were once used to describe, respectively, individuals with Down's syndrome and the syndrome itself. These terms are nowadays generally considered pejorative and inappropriate.