Definition of be under no illusion or illusions in English:

be under no illusion (or illusions)

Be fully aware of the true state of affairs.
More example sentences
  • She says she has been greatly impressed with the efficiency of the Dundee operation but is under no illusions about the challenges facing a factory on the northern fringes of Europe.
  • But I'm under no illusions, it could be taken away at any point, so I just grab it with both hands.
  • The 35-year-old is under no illusions about his situation.
See parent entry: illusion

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Word of the day flippant
Pronunciation: ˈflipənt
adjective
not showing a serious or respectful attitude