suddenly in WordNet English dictionary

1. quickly and without warning
   "he stopped suddenly"
   abruptly  suddenly  short  dead  abruptly  suddenly  short  dead 
   
2. happening unexpectedly
   "suddenly she felt a sharp pain in her side"
   suddenly  all of a sudden  of a sudden  suddenly  all of a sudden  of a sudden 
   
3. on impulse; without premeditation
   "he decided to go to Chicago on the spur of the moment"; "he made up his mind suddenly"
   on the spur of the moment  suddenly  on the spur of the moment  suddenly 
   

suddenly in English Wiktionary