U.S. President Donald Trump's denunciation of former FBI Director James Comey as a "slime ball" on Friday triggered a jump of 60,000 percent in look-ups for the word on the website of dictionary publisher Merriam-Webster's.

The disparaging term was among the top words looked up after Trump struck back over news reports that quoted Comey as harshly critical of the president in a memoir due to be published in the coming week, Merriam-Webster said.

Puzzled readers turned to their dictionaries after Trump wrote on Twitter that Comey was "a weak and untruthful slime ball who was, as time has proven, a terrible Director of the FBI." Within hours, "slimeball" had become the second-most-sought term on the dictionary website.