a. An elongated flexible unsegmented extension, as one of those surrounding the mouth of a sea anemone, used for feeling, grasping, or locomotion.
b. One of these structures in a cephalopod, typically being retractile and having a clublike end usually with suckers or hooks, in contrast to an arm, which is nonretractile and typically has suckers along the underside.
2. Botany One of the sensitive hairs on the leaves of certain insectivorous plants, such as a sundew.
3. A similar part or extension, especially with respect to the ability to extend influence, activity, or control: an espionage network with far-reaching tentacles.
[New Latin tentāculum, from Latin tentāre, to feel, try; see TENTATIVE.]
ten·tacu·lar (-tăkyə-lər) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.