Feeler (noun)

1. A thin, sensitive organ, typically one of a pair or series, used to feel or touch.
2. Something used to find out information or to test opinion.

Origin:

Late middle english: from old english fēler, from fēolan "to feel".

Examples:

1. The feelers of an ant are used to sense its environment.
2. The feelers on a caterpillar are used to feel its way around.
3. He put out feelers to gauge the company's interest in a merger.
4. She put out feelers to test the waters before making a decision.
5. The feelers on a snake are used to sense vibrations in the ground.