Rack, n. [Prob. fr. Icel. rek drift, motion, and akin to reka to drive, and E. wrack, wreck. √282.] Thin, flying, broken clouds, or any portion of floating vapor in the sky. Shak.
The winds in the upper region, which move the clouds above, which we call the rack,... pass without noise. Bacon.
And the night rack came rolling up. C. Kingsley.