circulator

1. A person or thing that causes something to circulate

   Who is the circulator of this rumor?

2. A local transit system that provides regular service within a closed loop

   You can ride the airport circulator to the next terminal.

3. A 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

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