Lookups on Merriam-Webster spiked on December 7, 2010.
President Obama used the word to describe fellow Democrats who objected to his compromise on extending tax cuts for wealthy Americans.
The president stated that a purist position would only allow Democrats to "feel good about ourselves and sanctimonious about how pure our intentions are."
Sanctimonious means "pretending to be morally superior to other people," or "hypocritically pious."
From the Latin word for "holiness," it shares a root with sanctify and sanction.