dormitive adjective 1noun 1forms 3phrases 2 adjective1 •Causing sleep.Quare Opium facit dormire: ... Quia est in eo Virtus dormitiva. (Why Opium produces sleep: ... Because there is in it a dormitive power.) — 1673 noun1 •A medicine to promote sleep; a soporific or opiate. formsdormitives · more dormitive · most dormitive Phrases with dormitive dormitive principleA type of tautology in which an item is explained in terms of the item itself, only put in different (usually more abstract) words. dormitive virtueA type of tautology in which an item is explained in terms of the item itself, only put in different (usually more abstract) words.