The word rector (from Latin, regere, "to rule") is used as the title of the priest or bishop who is in charge of a parish or in an administrative leadership position in a theological seminary or academy. It essentially translates the traditional Greek proistamenos, which means "the one who presides."
Rector is not used universally in English-speaking Orthodoxy, which usually simply uses the term parish priest or (in Greek parishes), proistamenos.