early 14c. (mid-13c. in place names), from Old Norse gap "chasm," related to gapa "to gape," from PIE *ghai- "to yawn, gape" (see yawn (v.)). Originally "hole in a wall or hedge;" broader sense is 16c. In U.S., common in place names in reference to a break or pass in a long mountain chain (especially one that water flows through). As a verb from 1847.
An opening in a structure or surface; a cleft or breach.
An interval or discontinuity in any series or sequence.
a rent or opening in a wall (Ezek. 13:5; comp. Amos 4:3). The false prophets did not stand in the gap (Ezek. 22: 30), i.e., they did nothing to stop the outbreak of wickedness.