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  1. lacking or not based on moral scruples or principles: an unprincipled person; unprincipled behavior.
  2. not instructed in the principles of something (usually followed by in).

Origin of unprincipled

First recorded in 1625–35; un-1 + principled
Related formsun·prin·ci·pled·ness, noun

Synonyms for unprincipled

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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for unprincipled


  1. lacking moral principles; unscrupulous
  2. (foll by in) archaic not versed in the principles of (a subject)
Derived Formsunprincipledness, noun
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

Word Origin and History for unprincipled

1630s, "not instructed" (in something), from un- (1) "not" + principled. Meaning "not honorable" is recorded from 1640s.

Online Etymology Dictionary, © 2010 Douglas Harper