NOUN (2)

1. something that acts like a tentacle in its ability to grasp and hold;
- Example: "caught in the tentacles of organized crime"

2. any of various elongated tactile or prehensile flexible organs that occur on the head or near the mouth in many animals; used for feeling or grasping or locomotion;

The Collaborative International Dictionary of English v.0.48:

Tentacle \Ten"ta*cle\, n. [NL. tentaculum, from L. tentare to
   handle, feel: cf. F. tentacule. See Tempt.] (Zool.)
   A more or less elongated process or organ, simple or
   branched, proceeding from the head or cephalic region of
   invertebrate animals, being either an organ of sense,
   prehension, or motion.
   [1913 Webster]

   Tentacle sheath (Zool.), a sheathlike structure around the
      base of the tentacles of many mollusks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tentacle
    n 1: something that acts like a tentacle in its ability to grasp
         and hold; "caught in the tentacles of organized crime"
    2: any of various elongated tactile or prehensile flexible
       organs that occur on the head or near the mouth in many
       animals; used for feeling or grasping or locomotion

The Jargon File (version 4.4.7, 29 Dec 2003):

tentacle
 n.

    A covert pseudo, sense 1. An artificial identity created in cyberspace
    for nefarious and deceptive purposes. The implication is that a single
    person may have multiple tentacles. This term was originally floated in
    some paranoid ravings on the cypherpunks list (see cypherpunk), and
    adopted in a spirit of irony by other, saner members. It has since shown
    up, used seriously, in the documentation for some remailer software, and is
    now (1994) widely recognized on the net. Compare astroturfing, sock
    puppet.