We don't have synonyms for specifiers yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are specified, specifier and specifies.
(n) :
(linguistics) A component of a phrase that is non-recursive and not found as a sister of the head of the phrase, but rather as a daughter of the maximal projection of the phrase.
(n) :
(linguistics) A component of a phrase that is non-recursive and not found as a sister of the head of the phrase, but rather as a daughter of the maximal projection of the phrase.