[uhn-der-mahyn or especially for 1, 2, 4, uhn-der-mahyn]
verb (used with object), undermined, undermining.
to injure or destroy by insidious activity or imperceptible stages, sometimes tending toward a sudden dramatic effect.
to attack by indirect, secret, or underhand means; attempt to subvert by stealth.
to make an excavation under; dig or tunnel beneath, as a military stronghold.
to weaken or cause to collapse by removing underlying support, as by digging away or eroding the foundation.

1300–50; Middle English underminen. See under-, mine2

underminer, noun
underminingly, adverb
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To undermine
World English Dictionary
undermine (ˌʌndəˈmaɪn)
1.  (of the sea, wind, etc) to wear away the bottom or base of (land, cliffs, etc)
2.  to weaken gradually or insidiously: their insults undermined her confidence
3.  to tunnel or dig beneath

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
Word Origin & History

c.1300, undermyne, from under + mine (v.). The fig. sense is attested from c.1430. Cf. Du. ondermijnen, Dan. underminere, Ger. unterminiren.
Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
Example sentences
And it happens to continue to help undermine the feudal underpinning in a
  really positive way.
One concern is that the findings of brain science will undermine our notion of
  autonomy and individual responsibility.
These smoldering underground fires generate pollution, undermine buildings and
  occasionally start surface fires.
Such an approach incorporates fatal efficiency flaws that undermine the process
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature