01 n. The act of opening.
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1.
The act of opening.[Obs.]
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2.
An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall.“An aperture between the mountains.” — Gilpin.“The back aperture of the nostrils.” — Owen.
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3.
The diameter of the exposed part of the object glass of a telescope or other optical instrument; as, a telescope of four-inch aperture.(Opt.)