Macron
Pronunciation : Ma"cron
Part of Speech : n.
Etymology : [NL., fr. Gr. (Pron.)
Definition : Defn: A short, straight, horizontal mark [-], placed over vowels to denote that they are to be pronounced with a long sound; as, a, in dame; e, in seam, etc.
Source : Webster's Unabridged Dictionary, 1913