vall- +

(Latin: wall, rampart; row or line of stakes)

circumvallate (verb), circumvallates; circumvallated; circumvallating
1. Surrounded by a trench or fossa or by a ridge as, for example, the circumvallate papillae on the tongue.
2. Surround with or as if with a rampart or other fortification.
3. To protect a town or camp by surrounding it with a rampart or a defensive wall.
circumvallation (s) (noun), circumvallations (pl)
1. A more or less continuous chain of redoubts and breastworks raised by besiegers outside the line of a besieged place to protect the besiegers from attacks from the outside; such as, by a relieving force.
2. A trench guarded with a parapet, constructed by besiegers, to secure themselves and check sallies of the besieged.
contravallation
A more or less continuous chain of redoubts and breastworks raised by besiegers outside the line of circumvallation of a besieged place to protect the besiegers from attacks from the outside, as by a relieving force.
interval
1. A space between two objects, points, or units.
2. The amount of time between two specified situations, events, or conditions; an intervening period of time: "There was an interval of 50 years before we saw our uncle again."
3. A period of temporary cessation; a pause: "There were intervals between the blasting sounds of the loud music."
4. One of a series of predetermined distances covered at regular time increments with intermittent periods of rest in an athletic workout.
5. In mathematics: a set of numbers consisting of all the numbers between a pair of given numbers along with either, both, or none of the endpoints; a closed interval, an open interval, a half-open interval, a line segment representing the set of numbers in an interval.
6. Chiefly British: an intermission, as between acts of a play.
7. In music, the difference, usually expressed in the number of steps, between two pitches.
obvallate
1. To surround with, or as with, a wall.
2. Walled-up, walled in, sealed up.
wall
1. A vertical structure forming an inside partition or an outside surface of a building.
2. A narrow upright structure, usually built of stone, wood, plaster, or brick, that acts as a boundary or keeps something in or out.
3. A structure of earth or stone built for defensive purposes.
4. Something similar to a wall in appearance or impenetrability: "The couple were met with a wall of reporters and photographers."
5. An obstacle to understanding or communication between people.
6. A vertical or nearly vertical rock face; such as, a sheer wall of granite.
7. A structure built as a barrier to flooding.
8. A membrane or lining enclosing or bounding an organ, blood vessel, or cavity of the body; as, the uterine wall.
9. In soccer, a line of defensive players who must stand at least ten yards from a free kick and who try to block a shot for a goal.
10. Etymology: from Latin vallum, "wall, rampart, row, or line of stakes"; apparently a collective form of vallus, "stake".