Definitions from Wordnet 2.0

• a cartridge containing an explosive charge but no bullet
• a figure representing the human form
• an ignorant or foolish person
• a person who does not talk
• make a dummy of; "dummy up the books that are to be published"
• having the appearance of being real but lacking capacity to function; "a dummy corporation"

Definitions from Wiktionary

• a person who does not talk ,
• an ignorant or foolish person ,
• a figure representing the human form ,
• a cartridge containing an explosive charge but no bullet