noun

• (figuratively) Imperfection; blemish on one’s reputation, stain.
  "1921, Warren G. Harding, Inaugural address, in Inaugural Addresses of the Presidents of the United States: from George Washington to Barack Obama, Washington, D.C.: U.S. G.P.O., 1989, There never can be equality of rewards or possessions so long as the human plan contains varied talents and differing degrees of industry and thrift, but ours ought to be a country free from the great blotches of distressed poverty."
• (slang) Blotting paper.

verb

• (transitive) To mark with blotches.
  "1770, Arthur Young, A Six Months Tour through the North of England, London: W. Strahan, Volume 2, p. 258, Upon the whole, the spirit and relief of the figures, with the strength of the colouring, render it a most noble picture; and it is not done in the coarse blotching stile, so common to the pieces which pass under the name of Bassan."
• (intransitive) To develop blotches, to become blotchy.
  "1878, Arthur Morecamp (pseudonym of Thomas Pilgrim), Live Boys; or, Charley and Nasho in Texas, Boston: Lee & Shepard, Chapter 17, p. 166, […] when a man is going to drive cattle out of the county he has to put a road-brand on them […] It is generally made of letters or figures, or something that won’t cross lines, because where they cross they are apt to blotch and then it’s hard to tell what the brand is and who the animal belongs to."