WordWeb Online

1. No longer in existence; lost or especially having died out leaving no living representatives
   "an extinct species of fish"; "an extinct royal family"; "extinct laws and customs"
   - nonextant
    
2. (of e.g. volcanos) permanently inactive
   "an extinct volcano"
    
3. Being out or having grown cold
   "threw his extinct cigarette into the stream"
   - out

See also: dead, extinction, nonexistent

Antonym: active, extant

Encyclopedia: Extinct