Definitions:

1. a copy that corresponds to an original exactly noun
   • The forms were long and required that the clerk make a duplicate for each set of files.
2. identically copied from an original adjective
   • a duplicate key
3. make a duplicate or duplicates of verb
   • Could you please duplicate this letter for me?

Synonyms:

• double
• duplication
• extra
• matching
• parallel
• twin