Definition of knock someone sideways in English:

knock someone sideways

phrasal verb

informal
  • Astonish someone.

    • ‘When they performed this on TOTP, I was knocked sideways.’
    • ‘But Preston were knocked sideways by the shock of seeing their impregnable lead suddenly wiped out.’
    • ‘The sheer wealth and size and richness of America knocked me sideways.’
    • ‘That said, most of what he plays washes over me these days - but once in a while, something comes along and knocks you sideways.’
    • ‘Every now and then, something came up which would completely knock you sideways.’
    overwhelm, overpower, stun, stupefy, amaze, astound, astonish, stagger, take someone's breath away, leave someone open-mouthed, dumbfound, confound, take aback
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