Green’s Dictionary of Slang

blackguardly adj.

shabby, dirty.

1883		William Morris reported in Illus. London News 10 Mar. 243/3: Almost all ordinary wares now made by man were shabbily and pretentiously ugly... Not even the pine-trees and gardens could make the men’s houses at Bournemouth tolerable. They were simply blackguardly; and even as he spoke they were being built by the mile [F&H].
1888		Salt Lake Herald (UT) 6 Oct. 6/3: One of the most blackguardly acts I have ever seen.
1895		Indep. (Honolulu, HI) 9 Sept. 2/3: The substitute [...] goes a little too far this morning in his blackguardly effusions against the Bishop [of Honolulu.
1905		N.Y. Tribune 1 Oct. 15/1: ‘If you take my advice you will [...] apologize for your blackguardly conduct.’ [...] ‘Oh, go to blazes!’.
1915		Eve. Star (Wash., DC) 7 Mar. 10/3: The duel was the immediate outcome of a harangue that Randolph delivered on March 30, 1826 [...] It has been described as ‘probably the most blackguardly speech ever heard in either branch of Congress’.
1920		Ogden Standard Examiner (UT) 24 Oct. 8/1: Miss Lucy was wholly ignorant of [...] the kind of man this blackguardly Prince really was.
1939		Dly Herald 19 Oct. 7/4: ‘You have committed the most wilful and blackguardly perjury,’ said Mr Justice Stable.