A line placed underneath a piece of text in order to provide emphasis or to indicate that it should be viewed in italics or (in electronic documents) that it acts as a hyperlink. / The character _.

To draw a line underneath something, especially to add emphasis; to underscore / (figuratively) To emphasise or stress something / (figuratively, obsolete) To influence secretly.

Passing under a railway line.

Underlining.

plural of underline

simple past tense and past participle of underline

plural of underliner

A liner or lining that goes underneath.

One who underlines.

A lining on the inside of a garment.