/bown"deuh ree, -dree/ , n. , pl. boundaries .
1. something that indicates bounds or limits; a limiting or bounding line.
2. Also called frontier . Math. the collection of all points of a given set having the property that every neighborhood of each point contains points in the set and in the complement of the set.
3. Cricket. a hit in which the ball reaches or crosses the boundary line of the field on one or more bounces, counting four runs for the batsman. Cf. six (def. 5).
[ 1620-30; BOUND 3 + -ARY ]
Syn. 1. BOUNDARY, BORDER, FRONTIER share the sense of that which divides one entity or political unit from another. BOUNDARY, in reference to a country, city, state, territory, or the like, most often designates a line on a map: boundaries are shown in red. Occasionally, it also refers to a physical feature that marks the agreed-upon line separating two political units: The Niagara River forms part of the boundary between the United States and Canada. BORDER is more often used than BOUNDARY in direct reference to a political dividing line; it may also refer to the region (of, for instance, a country) adjoining the actual line of demarcation: crossing the Mexican border; border towns along the Rio Grande.
FRONTIER may refer to a political dividing line: crossed the Spanish frontier on Tuesday. It may also denote or describe the portion of a country adjoining its border with another country ( towns in the Polish frontier ) or, especially in North America, the most remote settled or occupied parts of a country: the frontier towns of the Great Plains. FRONTIER, especially in the plural, also refers to the most advanced or newest activities in an area of knowledge or practice: the frontiers of nuclear medicine.