WordWeb Online

1. Not lit, or having grown cold
   "threw his extinct cigarette into the stream";
   - out
    
2. No longer in existence; lost or especially having died out leaving no living representatives
   "an extinct species of fish"; "extinct laws and customs";
   - nonextant
    
3. (of e.g. volcanoes) permanently inactive
   "an extinct volcano"

See also: dead, extinction, nonexistent

Antonym: active

Encyclopedia: Extinct