Definition of down adjective from the Oxford Advanced American Dictionary

     

    down

     adjective
    adjective
    NAmE//daʊn//
     
    [not before noun]
     
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  1. 1 (informal) sad or depressed I feel a little down today.
  2. 2(of a computer or computer system) not working The system was down all morning. see also downtime
  3. 3down with something (slang) to support or agree with someone or something “You going to the movies?” “Yeah, I'm down with that.”
  4. Idioms
    be down on your luck(informal)
     
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    to have no money because of a period of bad luck
    down in the mouth
     
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    unhappy and depressed
    hit somebody when they're down
     
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    to continue to hurt someone when they are already defeated
    kick somebody when they're down
     
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    to continue to hurt someone when they are already defeated, etc.
See the Oxford Advanced Learner's Dictionary entry: down