Verb

(undermin)

To dig underneath (something), to make a passage or for destructive or military purposes; to sap.

* 2009 , (Diarmaid MacCulloch), A History of Christianity , Penguin 2010, p. 312:

Martin, for instance, had on one occasion undermined a tree sacred to old gods, then stood in the path of its fall, but forced it to fall elsewhere by making the sign of the Cross.

(figuratively) To weaken or work against; to hinder, sabotage.

* {{quote-news, year=2012, date=April 19, author=Josh Halliday, work=the Guardian

, title= Free speech haven or lawless cesspool – can the internet be civilised? , passage=The growing use of social media to spread anger and dissent in the Arab world has been hailed by western governments as one of the chief justifications for a completely unfettered internet. The US is reportedly funding the secret rollout of technology in Iran in an effort to undermine internet censors in the country.}}

Verb

(deteriorat)

To make worse; to make inferior in quality or value; to impair.

to deteriorate the mind

* Southey

The art of war, like every other art, ecclesiastical architecture alone excepted, was greatly deteriorated during those years of general degradation

To grow worse; to be impaired in quality; to degenerate.

* {{quote-news

, year=2011 , date=January 8 , author=Paul Fletcher , title=Stevenage 3 - 1 Newcastle , work=BBC citation , page= , passage=It was turning into an abysmal afternoon for Newcastle and it deteriorated further when Tiote saw red for his challenge on Jon Ashton. }}