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 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.
• 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.

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