A tentacle was a flexible, elongated organ present in some species of animals or alien life forms
The Vendorians were known to have tentacles, as were the Ba'neth. (TOS: "The Survivor"), (VOY: "Riddles")
A symbiotic lifeform which managed to gain access to the Template:ShipClass starship Enterprise in 2152 snared several crewmembers with tentacles. (ENT: "Vox Sola")
In 2370, Julian Bashir was almost strangled by the tentacle of a metamorphic lifeform, actually a mutated Odo. Bashir injured the creature by cutting its tentacle with a laser scalpel. (DS9: "The Alternate")
In 2373, the tentacle of a creature grabbed Kira Nerys' hand when a serpent worm was delivered to Deep Space 9. (DS9: "A Simple Investigation")