- the region of a country bordering on another or a line, barrier, etc, marking such a boundary
- (as modifier): a frontier post
- US Canadian the edge of the settled area of a country
- (often plural) the limit of knowledge in a particular field: the frontiers of physics have been pushed back
WordReference Random House Learner's Dictionary of American English © 2026
fron•tier /frʌnˈtɪr/USA pronunciation
n. [countable]
adj. [before a noun]
WordReference Random House Unabridged Dictionary of American English © 2026- the border between two countries:the frontier crossing.
- land that forms the furthest regions of a country or territory.
- Often, frontiers. the limit of knowledge or the most advanced achievement in a particular field:the frontiers of medical research.
adj. [before a noun]
- of, relating to, or located on a frontier:a frontier town.
- See boundary.
fron•tier
(frun tēr′, fron-; also, esp. Brit., frun′tēr),USA pronunciation n.
adj.
fron•tier′less, adj.
fron•tier′like′, adj.
- the part of a country that borders another country;
boundary;
border. - the land or territory that forms the furthest extent of a country's settled or inhabited regions.
- Often, frontiers.
- the limit of knowledge or the most advanced achievement in a particular field:the frontiers of physics.
- an outer limit in a field of endeavor, esp. one in which the opportunities for research and development have not been exploited:the frontiers of space exploration.
- Mathematicsboundary (def. 2).
adj.
- of, pertaining to, or located on the frontier:a frontier town.
- Old French frontier, equivalent. to front (in the sense of opposite side; see front) + -ier -ier2
- Middle English frounter 1350–1400
fron•tier′like′, adj.
- 1. See boundary.
Collins Concise English Dictionary © HarperCollins Publishers::
frontier /ˈfrʌntɪə; frʌnˈtɪə/ n