Webster’s Revised Unabridged Dictionary · 1913
Lengthen
Length′en (-'n), v. t. [imp. & p. p. Lengthened (-'nd); p. pr. & vb. n. Lengthening (-'n·ĭng).] 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.
Length′en, v. i. To become longer. Locke.