/ ˈfrʌntɪə(r); NAmE frʌnˈtɪr/ noun
1.
( BrE ) [ C ] frontier (between A and B) | frontier (with sth) a line that separates two countries, etc.; the land near this line :
the frontier between the land of the Saxons and that of the Danes
a customs post on the frontier with Italy
a frontier town / zone / post
➡ note at border
2.
the frontier [ sing. ] the edge of land where people live and have built towns, beyond which the country is wild and unknown, especially in the western US in the 19th century :
a remote frontier settlement
3.
[ C , usually pl. ] frontier (of sth) the limit of sth, especially the limit of what is known about a particular subject or activity :
to push back the frontiers of science (= to increase knowledge of science)
to roll back the frontiers of government (= to limit the powers of the government)
••
WORD ORIGIN
late Middle English : from Old French frontiere , based on Latin frons , front- front.