(biochemistry) Ergocalciferol or calciferol; a constituent of vitamin D.

A twenty-percent (by volume) solution of dextrose, suitable for intravenous injection.

(dice games) A die with twenty sides.

(medicine) Initialism of difficult-to-treat.

(computing) Initialism of disk-to-tape: a method of data backup where information is copied from a disk (usually the hard disk of a computer) to a magnetic tape.