Mr. Macdonald is also very smart about playing dumb: “You know how people have opinions? I don’t got none,” he says in one setup on his special. Don’t be fooled: He does not have the vocabulary of a rube. When his jokes are punched up by an unusual or esoteric word, he isn’t showing off. It’s strategic.

When he mocks a waiter at a fancy restaurant — an utterly mundane target — his language adjusts to suit the character. “Guy shows up, and he’s got a big tray at a canted angle,” he says, employing an adjective that draws attention to itself before shifting into something similar to the overheated prose of an ad for a luxury product. “Every confection known to man is on it.”

Mr. Macdonald’s jokes aren’t just informed by word choice; they are often about it. He has a bit mocking metaphors and making the case for literal speech, and another that zeros in on the opening line of the Gettysburg Address to rib Lincoln gently for his use of the word “score.”

Sometimes his premises just seem like elaborate excuses to say a phrase that tickles him. In the middle of exploring the idea that beauty is in the eye of the beholder, he finds himself searching onstage for another way to say “beauty,” and what he comes up with — “optic trick” — is the highlight of the entire joke, a term with a strong point of view and a pair of rhyming consonant sounds that echo off each other.

On “Saturday Night Live,” Mr. Macdonald could come off as just another sarcastic wise guy with an ironic attitude, a humbler Dennis Miller. And the content of his stand-up right now is pretty banal stuff, often from the well-worn perspective of an older guy marveling at how technology or fame or dining has changed since he was young. But listen to enough of his comedy, and what becomes clear is this ordinary fella has an aesthete’s attention to form.

“Hitler’s Dog” starts in the middle of a joke — comedy in medias res, to use a fancy term he might try out — and it ends abruptly. In bookending his show this way, Mr. Macdonald not only toys with the meaning of a joke, but he also drives home the point that the part can be funnier than the whole.