stammer

But this stammering, rather dull chap doesn’t come across as a genius.

At this the man blushed and stammered so much, he could barely find the key to the royal suite, but at last he did.

Miss Mortimer stammered, flummoxed, for this was not the sort of reply one would expect from a Swanburne girl.

“I—I cannot say, my lady,” Penelope stammered.

After one of his sketches, the actual Sid Caesar might ever so briefly, in a stammering voice, appear before a commercial break to say: “We’ll be right back.”