Definify.com

Webster 1828 Edition

ppr.

Marking with a line below.

underlining

underlining ‎(plural underlinings)

An act or instance of marking text with an underline.
- 2005, Theodore Cheney, Getting the Words Right (page 238)
  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.
A lining on the inside of a garment.