Definition from Wiktionary, the free dictionary
- Movement ahead or forward.
- (nautical) Forward motion, or its rate.
- (countable, transport) The interval of time or distance between the fronts of two vehicles (e.g. buses) moving in succession in the same direction, especially along the same pre-determined route.
- (uncountable, figuratively) Progress toward a goal.
- (countable) The clearance beneath an object, such as an arch, ceiling or bridge; headroom.
- (coal-mining) A cross-heading.
Derived terms 
Clearance beneath an object
Time or distance interval between the fronts of two vehicles