feeler

definition: one of a pair of mobile appendages on the head of e.g. insects and crustaceans
example:
speech part: noun
synonyms: antenna
definition: slender tactile process on the jaws of a fish
example:
speech part: noun
synonyms: barbel
definition: sensitivity similar to that of a receptor organ
example:
speech part: noun
synonyms: antenna
definition: a tentative suggestion designed to elicit the reactions of others
example:
speech part: noun
synonyms: advance

How feeler is being used?