We don't have synonyms for prefire yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are prehire, prefine and refire.
(v) :
Alternative form of pre-fire. [(video games, intransitive) To shoot at the anticipated location of another player before they are visible or within range.]
(v) :
Alternative form of pre-fire. [(video games, intransitive) To shoot at the anticipated location of another player before they are visible or within range.]