"I never suggest," returned Mr. Jackson imperturbably.
"It’s an unlikely name for a New York telegraph office; at least in this quarter," an unexpected voice observed; and turning around Archer saw Lawrence Lefferts at his elbow, pulling an imperturbable moustache and affecting not to glance at the message.
There are no more uses of "imperturbable" in the book.
Show samples from other sources
Silas was imperturbable.
Neil Gaiman -- The Graveyard Book
Out of loudspeakers all around Zollverein, the staccato voice of the Reich grows like some imperturbable tree; its subjects lean toward its branches as if toward the lips of God.