Definition of "grimy"

Then came a maid with hand-bag and shawls, and after her a tall young lady. She stood for a moment holding her skirt above the grimy steps, […] , and the light of the reflector fell full upon her.

1897 December (indicated as 1898), Winston Churchill, chapter V, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd.

Riffs from older songs seem to be more popular, as only two from the past decade made it into the top 20. They were Muse's Plug In Baby, at 11, and The White Stripes' grimy Seven Nation Army at 15.

2009 November 27, “Jimi Hendrix's Voodoo Child has 'best guitar riff'”, in BBC