noun

• (uncountable) The nature or property that gives rise to revulsion or inspires loathing.
  "For my part I would rather counſell you to deſtroy your Rattes and Miſe with Traps, Banes, or Weeſels: for beſides the ſluttiſhneſſe ⁊ lothſomeneſſe of the Catte (you know what ſhe layes in the Malt heape) ſhe is moſt daungerous and pernicious among children, as I mee ſelf haue had good experience."
• (countable) A loathsome thing.
  "H. P. Lovecraft After it raced the naked, tittering, phosphorescent thing that belonged on the carven pedestal, and still farther behind panted the dark men, and all the dread crew of sentient loathsomenesses. The corpse was gaining on its pursuers …"