1. Anything of great importance or consequence
   "Graduating from college was a big deal for her family"
    
2. An important influential person
   "she's a big deal in local politics";
   - big shot [informal], big gun [informal], big wheel [N. Amer, informal], big cheese [informal], big enchilada [informal], big fish [informal], head honcho [N. Amer, informal], big noise [informal], big name [informal]

Type of: importance, importancy [archaic], important person, influential person, personage