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.

In or at a lower level than; in the area covered or surmounted by. / Below the surface of. / From one side of to the other, passing beneath. / Less than.

In or to a lower or subordinate position, or a position beneath or below something, physically or figuratively. / So as to pass beneath something. / (usually in compounds) Insufficiently.

Lower; beneath something. / In a state of subordination, submission or defeat. / (medicine, colloquial) Under anesthesia, especially general anesthesia; sedated.

The amount by which an actual total is less than the expected or required amount.

(not comparable) Below the ground; below the surface of the Earth. / (figuratively) Hidden, furtive, secretive.

Below the ground. / Secretly.

(geography) Regions beneath the surface of the earth, both natural (eg. caves) and man-made (eg. mines). / (chiefly Britain) Synonym of subway: a railway that is under the ground.

To route electricity distribution cables underground.