Unobstructed space required for occasional removal of parts of equipment.

1. In a piston-and-cylinder mechanism, the space at the end of the cylinder when the piston is at dead-center position toward the end of the cylinder.

2. The ratio of the volume of this space to the piston displacement during a stroke.

The space between the top or side of a car and the roof or wall.

1. The clear space between a vessel and an object such as a navigation light, hazard to navigation, or another vessel.

2. A specific message from air-traffic control to a pilot of an aircraft allowing him to proceed in accordance with the flight plan which the pilot had filed, or with some modification of the original plan.

3. In the instrument landing system, the difference in the depth of modulation which is required to produce a full-scale deflection of the course deviation indicator needle in any flight sector outside the on-course sectors.

Elevation of a gun at such an angle that a projectile will not strike an obstacle between the muzzle and the target.

The annular space between down-hole drill-string equipment, such as bits, core barrels, and casing, and the walls of the borehole with the down-hole equipment centered in the hole.