Easton's Bible Dictionary
A raised road for public use. Such roads were not found in Palestine; hence the force of the language used to describe the return of the captives and the advent of the Messiah (Isaiah 11:16; 35:8; 40:3; 62:10) under the figure of the preparation of a grand thoroughfare for their march.
During their possession of Palestine the Romans constructed several important highways, as they did in all countries which they ruled.
Noah Webster's New International Dictionary of the English Language
(n.) A road or way open to the use of the public; a main road or thoroughfare.