from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A diacritical mark placed above a vowel to indicate a long sound or phonetic value in pronunciation, such as (ā) in the word make.
- n. The horizontal mark ( ¯ ) used to indicate a stressed or long syllable in a foot of verse.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A short, straight, horizontal diacritical mark (¯) placed over any of various letters. It usually is used to indicate that the pronunciation of the vowel is long, in Mandarin pinyin (Chinese), it indicates the first tone, e.g. chūzūchē.
from the GNU version of the Collaborative International Dictionary of English
- n. A short, straight, horizontal mark [-], placed over vowels to denote that they are to be pronounced with a long sound; as, ā, in dāme; ē, in sēam, etc.
from The Century Dictionary and Cyclopedia
- n. In grammar, a short horizontal line placed over a vowel to show that it is long in quantity, or, as in English, has a “long” sojnd: opposed to the breve, or mark of a short vowel.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a diacritical mark (-) placed above a vowel to indicate a long sound
Greek makron, from neuter of makros, long; see māk- in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)
From the Ancient Greek μακρόν (makron), neuter form of μακρός (makros, "long") (English macro-). (Wiktionary)