at ones peril

from The Collaborative International Dictionary of English v.0.48
Peril \Per"il\, n. [F. p['e]ril, fr. L. periculum, periclum,
   akin to peritus experienced, skilled, and E. fare. See
   {Fare}, and cf. {Experience}.]
   Danger; risk; hazard; jeopardy; exposure of person or
   property to injury, loss, or destruction.
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         In perils of waters, in perils of robbers. --2 Cor. xi.
                                                  26.
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         Adventure hard
         With peril great achieved.               --Milton.
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   {At one's peril}, or {On one's peril}, with risk or danger to
      one; at the hazard of. "On thy soul's peril." --Shak.
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   Syn: Hazard; risk; jeopardy. See {Danger}.
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