indicator

1. (chemistry) Any of many substances, such as litmus, used to indicate the concentration of a substance, or the degree of a reaction.

2. (ecology) A plant or animal whose presence is indicative of some specific environment.

3. (economics) A measure, such as unemployment rate, which can be used to predict economic trends.

4. (UK, Australia, New Zealand, Ireland, South Africa, automotive) A turn signal; each of the flashing lights on each side of a vehicle which indicate a turn is being made to left or right, or a lane change etc.Synonyms: blinker, directional, directional signal, direction indicator, trafficator, turn indicator, turn signalAustraliaIrelandNew-ZealandSouth-AfricaUK

5. (crosswording) A codeword that marks the use of a specific cryptic device.Examples: "'Wild' is an anagram indicator showing that the letters of 'danger' have to be rearranged."; "We surrounded the strike, Snowy (5) Snowy is the definition in this clue. Ignore the punctuation and capital letter of Snowy! Surrounded is the container indicator."; "We have already mentioned 'in' having multiple uses; 'round' or 'around' might be a container indicator or a reversal indicator; 'without' might be a container indicator or a deletion indicator, and so on."