to mark with a line or lines underneath; underscore.

to indicate the importance of; emphasize, as by stressing or italicizing.

Printing . a caption under an illustration.

a line drawn under something; an underscore.

verb

accentuate , bracket , call attention to , caption , check off , draw attention to , feature , give emphasis , highlight , indicate , interlineate , italicize , play up , point to , point up , rule , stress , underscore , accent , ascent , emphasize , mark