1. An air gap between a wing and the length of a slat or certain other auxiliary airfoils, the gap providing space for airflow or room for the auxiliary airfoil to be depressed in such a manner as to make for smooth air passage on the surface.

2. Any of certain narrow apertures made through a wing to improve aerodynamic characteristics.

A punched-out area of a hand-sorted card to connect two or more guide holes; slots can be extended to the outside edge with notches.

A narrow, vertical opening.

One of the conductor-holding grooves in the face of the rotor or stator of an electric rotating machine.

To hole; to undercut or channel.