shim

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

• noun A thin, often tapered piece of material, such as wood, stone, or metal, used to fill gaps, make something level, or adjust something to fit properly.
• transitive verb To fill in, level, or adjust by using shims or a shim.

from The Century Dictionary.

• noun A white spot, as a white streak on a horse's face.
• noun An ignis fatuus.
• Same as shime.
• noun An imperfect shingle, thicker at one side than the other; also, an imperfect stave for a bucket.
• To wedge up or fill out to a fair surface by inserting a thin wedge or piece of material.
• noun Broadly, in machinery, a thin slip (usually of metal, but often of other material) used to fill up space caused by wear, or placed between parts liable to wear, as under the cap of a pillow-block or journal-box.
• noun In stone-working and quarrying, a plate used to fill out the space at the side of a jumper-hole, between it and a wedge used for separating a block of stone, or for contracting the space in fitting a lewis into the hole.
• noun A shim-plow (which see, under plow).

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

• noun A kind of shallow plow used in tillage to break the ground, and clear it of weeds.
• noun (Mach.) A thin piece of metal placed between two parts to make a fit.

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

• noun A wedge.
• noun A thin piece of material, sometimes tapered, used for alignment or support.
• noun computing A small library that transparently intercepts and modifies calls to an API, usually for compatibility purposes.
• noun A kind of shallow plow used in tillage to break the ground and clear it of weeds.
• noun A small metal device used to pick open a lock.
• verb To fit one or more shims to a piece of machinery
• verb To adjust something by using shims
• noun informal, often derogatory a person characterised by both male and female traits, or by ambiguous male-female traits, also called a he-she; transsexual.
• noun informal, often derogatory hermaphrodite.

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

• noun a thin wedge of material (wood or metal or stone) for driving into crevices