Weegy: in·di·ca·tor (nd-ktr)
1. One that indicates, especially:
a. A pointer or an index.
b. An instrument used to monitor the operation or condition of an engine, furnace, electrical network, reservoir, or other physical system; a meter or gauge.
c. [ The needle, dial, or other registering device on such an instrument.
2. Chemistry Any of various substances, such as litmus or phenolphthalein, that indicate the presence, absence, or ... (More)