"gratings" in the noun sense
1. grate, grating
a barrier that has parallel or crossed bars blocking a passage but admitting air
2. grate, grating
a frame of iron bars to hold a fire
3. diffraction grating, grating
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
Source: WordNet® (An amazing lexical database of English)
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