Passing under a railway line.
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 emphasise or stress something
To draw a line underneath something, especially to add emphasis; to underscore
To underestimate, or assign too low a value to.
To have too little regard for.
An undervaluation; a price or rate below the actual worth.