Adverbial high up has 1 sense
  1. high, high up - at a great altitude; "he climbed high on the ladder"
,Noun high up has 1 sense
  1. very important person, VIP, high-up, dignitary, panjandrum, high muckamuck - an important or influential (and often overbearing) person
    --1 is a kind of important person, influential person, personage
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