1.NounA person or thing that causes something to circulate
"Who is the circulator of this rumor?"
2.NounA local transit system that provides regular service within a closed loop
"You can ride the airport circulator to the next terminal."
3.NounA passive electronic component with three or more ports, in which the ports can be accessed in such a way that when a signal is fed into any port it is transferred to the next port only