Definition of "marring"

[…] Hath all his ventures fail'd? What, not one hit?From Tripolis, from Mexico, from England,From Lisbon, Barbary, and India?And not one vessel scape the dreadful touchOf merchant-marring rocks?

c. 1596–1598 (date written), William Shakespeare, “The Merchant of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act III, scene ii]

Unable to read even as much of them as the scamps who wrote them and could read nothing more, the smuggler had finally trained himself to ignore them; they were marrings to be overlooked while the eye was out for other, more meaningful detail.

1985, Samuel R. Delany, Flight from Nevèrÿon