a combining form with the meanings âheight,â âtip end,â âextremities of the body,â used in the formation of compound words: acrophobia. Also, especially before a vowel, acr-. Origin of acro-. < Greek, combining form of Ã¡kros topmost, highest; akin to Latin Äcer sharp.
â¢ CANTUS FIRMUS (noun) The noun CANTUS FIRMUS has 1 sense: 1. a melody used as the basis for a polyphonic composition. Familiarity information: CANTUS FIRMUS used as a noun is very rare. Dictionary entry details.
Definition of cantus firmus. 1  1 : the plainsong or simple Gregorian melody originally sung in unison and prescribed as to form and use by ecclesiastical tradition. 2  2 : a melodic theme or subject; especially : one for contrapuntal treatment.