grating

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

• noun A grill or network of bars set in a window or door or used as a partition; a grate.
• noun A diffraction grating.

from The Century Dictionary.

• noun A partition or frame of parallel or crossing bars; an open latticework of wood or metal serving as a cover or guard, but admitting light, air, etc., as in the fair-weather hatches of a ship, the cover of the mouth of a drain or sewer, etc.
• noun In optics: An arrangement of parallel wires in a plane, designed to produce spectra by diffraction: specifically called a real grating.
• noun A series of fine parallel lines on a surface of glass or polished metal ruled very close together, at the rate of 10,000 to 20,000, or even 40,000, to the inch: distinctively called a diffraction or diffractive grating.
• noun A timber framework consisting of beams which cross one another at right angles to support the foundation of a heavy building in light, loose soil.
• noun In metallurgy, the act of separating large from small ore. See grate, n.
• noun The act of rubbing harshly; the harsh sound caused by the rasping or scraping of hard, rough bodies; the feeling produced by harsh attrition.
• Harsh; rasping; fretting; irritating: as, grating sounds; a grating temper.

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

• adjective That grates; making a harsh sound; harsh.
• noun A partition, covering, or frame of parallel or cross bars; a latticework resembling a window grate.
• noun (Optics) A system of close equidistant parallel lines or bars, esp. lines ruled on a polished surface, used for producing spectra by diffraction; -- called also diffraction grating.
• noun (Naut.) The strong wooden lattice used to cover a hatch, admitting light and air; also, a movable Lattice used for the flooring of boats.
• noun A harsh sound caused by attrition.

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

• adjective harsh and unpleasant
• noun A barrier that has parallel or crossed bars blocking a passage but admitting air.
• noun A frame of iron bars to hold a fire
• verb Present participle of grate.

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

• adjective unpleasantly harsh or grating in sound
• noun optical device consisting of a surface with many parallel grooves in it; disperses a beam of light (or other electromagnetic radiation) into its wavelengths to produce its spectrum
• noun a frame of iron bars to hold a fire
• noun a barrier that has parallel or crossed bars blocking a passage but admitting air