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-proof

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  1. a combining form meaning “resistant, impervious to” that specified by the initial element: burglarproof; childproof; waterproof.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for -proof

-proof

adjective, combining form
  1. secure against (damage by); (make) impervious towaterproof; mothproof; childproof

Word Origin

from proof (adj)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012