Definition of dummy noun from the Oxford Advanced Learner's Dictionary
dummy
noun
ˈdʌmi ˈdʌmi
pluraldummies1[countable]a model of a person, used especially when making clothes or for showing them in a shop windowa tailor's dummya ventriloquist's dummy see also mannequin (2)2[countable]a thing that seems to be real but is only a copy of the real thingThe bottles of whisky on display are all dummies.3[countable] (North American English, informal) a stupid personDon't just stand there, you dummy.4[countable] (in some sports) an occasion when you pretend to make a particular move and then do not do so5[countable] (British English) (North American Englishpacifier)a specially shaped rubber or plastic object for a baby to suck6[uncountable] (in card games, especially bridge) the cards which are placed facing upwards on the table and which can be seen by all the playersShe played a jack from dummy.