We don't have synonyms for macrons yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are macron, macros and matrons.
(n) :
(orthography) A short, straight, horizontal diacritical mark (◌̄) placed over a letter, usually to indicate that the pronunciation of a vowel is long.
(n) :
(orthography) A short, straight, horizontal diacritical mark (◌̄) placed over a letter, usually to indicate that the pronunciation of a vowel is long.