underlining

verb

1. (form-of, gerund, participle, present)present participle and gerund of underline

noun

1. (countable, uncountable)An act or instance of marking text with an underline.

   “There are so many underlinings, so many exclamation points in the margins, and so much highlighting from my many readings and appreciatings that it looks like a case of severe book abuse. It is not; these are marks of love.”

2. A lining on the inside of a garment.