Webster's Revised Unabridged Dictionary · 1913

Lengthen

Lengthen (-'n) , transitive verb

To extent in length; to make longer in extent or duration; as, to lengthen a line or a road; to lengthen life; -- sometimes followed by out.
What if I please to lengthen out his date. — Dryden

Lengthen , intransitive verb

To become longer. — Locke