Any high wall for defense.
In fortification: an indented parapet, formed by a series of rising members called cops or merlons, separated by openings called crenelles or embrasures, the soldier sheltering himself behind the merlon while he fires through the embrasure or through a loophole in the battlement.
The towering roof of heaven.
A temporary fortification built by troops in the field; a defensive earthwork in the field.
The collection of raw data in the field, field research, field study, field studies.
Work done out in the fields as opposed to that done elsewhere on the farm (e.g., barn, house, outbuildings, office).
Work done out in the real world rather than in controlled conditions