Eyesore

(n.) Something offensive to the eye or sight; a blemish.

Thesaurus Entries

baboon, bag, blemish, bloodstain, blot, blotch, blur, brand, dab, daub, dog, fleck, flick, flyspeck, fright, gargoyle, hag, harridan, macula, maculation, macule, mark, mess, monster, monstrosity, no beauty, patch, scarecrow, sight, smear, smirch, smouch, smudge, smut, smutch, spatter, speck, speckle, splash, splatter, splotch, spot, stain, stigma, taint, tarnish, teratism, ugly duckling, witch