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explain away

British  

verb

  1. (tr, adverb) to offer excuses or reasons for (bad conduct, mistakes, etc)

"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

explain away Idioms  
  1. Dismiss or minimize the importance of something, especially something detrimental. For example, “His words were taken down, and though he tried to explain them away, he was sent to the Tower” (Thomas Macaulay, The History of England, 1855). [c. 1700]