From dumb + -y.

• IPA: /ˈdʌmi/

dummy (plural dummies)

1. (dated) A silent person; a person who does not talk.

   Synonyms: dumby

   Coordinate term: mute

2. A stupid person.

   Synonyms: dumby, dumdum

   Coordinate terms: half-wit, idiot

   Don't be such a dummy!

3. (AAVE, Baltimore, slang) A term of address.

   Synonyms: dude, bro

   Coordinate term: stupid

   Hey dummy, what's good wit chu?

4. A figure of a person or animal used by a ventriloquist; a puppet.
5. Something constructed with the size and form of a human, to be used in place of a person.

   Synonyms: mannequin, marionette

   To understand the effects of the accident, we dropped a dummy from the rooftop.

6. A person who is the mere tool of another; a man of straw.
7. A deliberately nonfunctional device or tool used in place of a functional one.

   The hammer and drill in the display are dummies.

   • 1950, National Bureau of Standards Miscellaneous Publication, page 138:

     The second method was to use two loadometers under the wheels of one axle, mounting the wheels of the other axle on what we called "equalizing blocks" or "dummies." By that method the two axles are brought into the same horizontal plane […]

8. (AU, UK, NZ) A "dummy teat"; a plastic or rubber teat used to soothe or comfort a baby; a pacifier. [from 20th c.]

   Synonyms: Thesaurus:pacifier

   The baby wants her dummy.

   • 2008, Bern, Bern's Fairy Tales‎^{[http://books.google.com.au/books?id=AYro8LGJi0kC&pg=PA15&dq=%22dummy%22%7C%22dummies%22+baby+-intitle:%22dummies%22+-inauthor:%22%22&hl=en&sa=X&ei=jIRHT6WbEs-ZiAeduNWPDg&redir_esc=y#v=onepage&q=%22dummy%22%7C%22dummies%22%20baby%20-intitle%3A%22dummies%22%20-inauthor%3A%22%22&f=false]}, page 15:

     No Fairy baby has ever been seen to suck its thumb or to use a dummy.

9. (card games, chiefly, bridge) A player whose hand is shown and is to be played from by another player.
10. (linguistics) A word serving only to make a construction grammatical.

    The pronoun "it" in "It's a mystery why this happened" is a dummy.

11. (programming) An unused parameter or value.

    If flag1 is false, the other parameters are dummies.

12. (sports, mostly, rugby, soccer) A feigned pass or kick or play in order to deceive an opponent.
13. (sports, UK) A bodily gesture meant to fool an opposing player; a feint.

    Synonyms: juke

14. (attributive) A newborn animal that is indifferent to stimulus and does not voluntarily move.

    a dummy calf, lamb, or foal

• (silent person) dumb
• (stupid person) dumb

• French: muet
• Italian: taciturno
• Russian: молчу́н
• Spanish: silencioso

• French: idiot, idiote, imbécile
• Italian: stupido, scemo
• Portuguese: idiota, imbecil
• Russian: дура́к
• Spanish: tonto

• German: Puppe

• French: mannequin
• Italian: manichino, sagoma, fantoccio
• Portuguese: manequim
• Russian: манеке́н
• Spanish: maniquí

• German: Attrappe
• Italian: simulacro
• Portuguese: simulacro
• Russian: маке́т

• French: mort
• Italian: morto
• Russian: болва́н
• Spanish: muerto

• Russian: финт

dummy (dummies, present participle dummying; simple past and past participle dummied)

1. To make a mock-up or prototype version of something, without some or all off its intended functionality.

   The carpenters dummied some props for the rehearsals.

2. (sports) To feint.

   Synonyms: juke

dummy

1. (US, slang) Extremely.

   It's dummy hot outside.