A long, narrow ditch or hole dug in the ground.

A narrow excavation as used in warfare, as a cover for besieging or emplaced forces.

A pit, usually rectangular with smooth walls and floor, excavated during an archaeological investigation.

(usually followed by upon) To invade, especially with regard to the rights or the exclusive authority of another; to encroach.

(infantry) To excavate an elongated pit for protection of soldiers and or equipment, usually perpendicular to the line of sight toward the enemy.

To excavate an elongated and often narrow pit.

The front line of any field of endeavor, as the line of scrimmage in American football, patrol duty for a policeman.