It was a remarkable term for the president to use to describe a legal process laid out in the Constitution.

Mr. Trump’s Twitter outburst comes as pressure builds with the stream of testimony from current and former administration officials about his efforts to use the power of the White House for personal gain.

The president regularly uses his Twitter feed to make hyperbolic declarations, but he has not used the term “lynching” in a tweet since 2015, during the Republican primary campaign. The president’s use of the word Tuesday drew immediate criticism.

“You think this impeachment is a LYNCHING? What the hell is wrong with you,” Representative Bobby L. Rush, Democrat of Illinois and a former Black Panther leader, said in a Twitter post.

“I know the history of that word,” Representative James E. Clyburn, Democrat of South Carolina and the House majority whip, said on CNN Tuesday. “That is a word that we ought to be very, very careful about.”