stylet

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A slender, pointed instrument or weapon, such as a stiletto.
• noun A surgical probe.
• noun A fine wire that is run through a catheter, cannula, or hollow needle to keep it stiff or clear of debris.
• noun Zoology A small, stiff, needlelike organ or appendage, such as a piercing mouthpart of an aphid or other hemipteran insect.

from The Century Dictionary.

• noun A slender pointed instrument; a stiletto.
• noun In surgery, the perforator of a trocar; the stiffening wire or rod in a flexible catheter; sometimes, a probe. Also stilette.
• noun In zoology, a little style; also, a style; specifically, in entomology, one of the second of the t hree pairs of rhabdites or appendages of the abdominal sternites entering into the formation of the ovipositor. See cut under Arctisca.
• noun Specifically— Same as cercopod. Compare style, 2 .
• noun In fishes, one of the slender rays of bone on or above the base of the ribs; the epipleural.

from the GNU version of the Collaborative International Dictionary of English.

• noun A small poniard; a stiletto.
• noun An instrument for examining wounds and fistulas, and for passing setons, and the like; a probe, -- called also specillum.
• noun A stiff wire, inserted in catheters or other tubular instruments to maintain their shape and prevent clogging.
• noun (Zoöl.) Any small, more or less rigid, bristlelike organ.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A slender medical probe or device.
• noun zoology A stiff, slender organ of an animal.
• noun botany A style of a plant's flower.
• noun A stiletto or poniard.
• noun An engraving tool.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun small needlelike appendage; especially the feeding organ of a tardigrade