A brilliant idea. This cliché, in which stroke betokens the sudden appearance of the idea, dates from the second half of the 1800s and at first was always used admiringly. Thus the Tacoma News of December 13, 1889, stated, “The latest nickel-in-the slot scheme is really a stroke of genius and is destined to revolutionize cheap literature in this country.” Later, however, the term was often used sarcastically, as in “You forgot the tickets? That was a stroke of genius.”