self-poˈssessing,ppl.a.rare. [f. after next.] = self-possessed. 1789Burke Corr. (1844) III. 20 To dare to be fearful, when all about you are full of presumption and confidence..discovers a self-possessing and collected character.1863M. Brydie Tabl. Geol., etc. 54 A quiet, self-possessing mind.