Definition of have on phrasal verb from the Oxford Advanced Learner's Dictionary

  

have on

 phrasal verb
phrasal verb
 
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Phrasal Verbs
(informal) to try to make somebody believe something that is not true, usually as a joke You didn't really, did you? You're not having me on, are you?

    have (got) something on

    (not used in the progressive tenses)
     
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  1. 1  to be wearing something She had a red jacket on. He had nothing (= no clothes) on.
  2. 2to leave a piece of equipment working She has her TV on all day.
  3. 3  to have arranged to do something I can't see you this week—I've got a lot on.

have (got) something on somebody

 
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[no passive] (informal) (not used in the progressive tenses) to know something bad about somebody, especially something that connects them with a crime I'm not worried—they've got nothing on me.
See the Oxford Advanced American Dictionary entry: have on