Entry 1 sense Webster, 1913 Dormant /dôr'-mənt/ · Dor·mant · IPA /ˈdɔɹmənt/ 01 n. A large beam in the roof of a house upon which portions of the other timbers rest or “ sleep.” 1. A large beam in the roof of a house upon which portions of the other timbers rest or “ sleep.”(Arch.)