From The Collaborative International Dictionary of English v.0.48 [gcide]: Grate \Grate\, v. t. [imp. & p. p. Grated; p. pr. & vb. n. Grating.] To furnish with grates; to protect with a grating or crossbars; as, to grate a window. [1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]: Grating \Grat"ing\, a. [See Grate to rub harshy.] That grates; making a harsh sound; harsh. -- Grat"ing*ly, adv. [1913 Webster] From The Collaborative International Dictionary of English v.0.48 [gcide]: Grating \Grat"ing\, n. A harsh sound caused by attrition. [1913 Webster] From The Collaborative International Dictionary of English v.0.48 [gcide]: Grating \Grat"ing\, n. [See 2d Grate.] 1. A partition, covering, or frame of parallel or cross bars; a latticework resembling a window grate; as, the grating of a prison or convent. [1913 Webster] 2. (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. Note: Gratings have been made with over 40,000 such lines to the inch, but those with a somewhat smaller number give the best definition. They are used, e. g., to produce monochromatic light for use in optical instruments such as spectrophotometers. [Webster 1913 Suppl.] 3. pl. (Naut.) The strong wooden lattice used to cover a hatch, admitting light and air; also, a movable Lattice used for the flooring of boats. [1913 Webster] From WordNet (r) 3.0 (2006) [wn]: grating adj 1: unpleasantly harsh or grating in sound; "a gravelly voice" [syn: grating, gravelly, rasping, raspy, rough, scratchy] n 1: a barrier that has parallel or crossed bars blocking a passage but admitting air [syn: grate, grating] 2: a frame of iron bars to hold a fire [syn: grate, grating] 3: 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 [syn: diffraction grating, grating]