From The Collaborative International Dictionary of English v.0.48:
Gap \Gap\ (g[a^]p), n. [OE. gap; cf. Icel. gap an empty space, Sw. gap mouth, breach, abyss, Dan. gab mouth, opening, AS. geap expanse; as adj., wide, spacious. See Gape.] 1. An opening in anything made by breaking or parting; as, a gap in a fence; an opening for a passage or entrance; an opening which implies a breach or defect; a vacant space or time; a hiatus; a mountain pass. [1913 Webster]
Miseries ensued by the opening of that gap. --Knolles. [1913 Webster]
It would make a great gap in your own honor. --Shak. [1913 Webster]
2. (A["e]ronautics) The vertical distance between two superposed surfaces, esp. in a biplane. [Webster 1913 Suppl.]
Gap lathe (Mach.), a turning lathe with a deep notch in the bed to admit of turning a short object of large diameter.
To stand in the gap, to expose one's self for the protection of something; to make defense against any assailing danger; to take the place of a fallen defender or supporter.
To stop a gap, to secure a weak point; to repair a defect. [1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Gap \Gap\, v. t. 1. To notch, as a sword or knife. [1913 Webster]
2. To make an opening in; to breach. [1913 Webster]
Their masses are gapp'd with our grape. --Tennyson. [1913 Webster]