PortassPor"tass\, n. [OF. porte-hors a kind of prayer book, so called from being portable; cf. LL. portiforium.] A breviary; a prayer book. [Written variously portace, portasse, portesse, portise, porthose, portos, portus, portuse, etc.] [Obs.] --Spenser. Camden. By God and by this porthors I you swear. --Chaucer.