Vine's Expository Dictionary of NT Words 
"a space lying between two limits, a country, land," is translated "region" in Matthew 4:16; Luke 3:1; Acts 8:1; 13:49; 16:6; 18:23 , RV. In the last three passages it has the technical sense of a subdivision of a Roman province, Lat. regio; as also No. 2 in Acts 14:6 . See Country , No. 3.
"a country or region round about" (peri), is translated "region round about" in Matthew 3:5; 14:35 , RV; Mark 1:28 (in some mss. Mark 6:55 ); Luke 3:3 , RV; 4:14; 4:37, RV; 7:17; Acts 14:6 (see No. 1). See Country , No. 4.
"an inclination, slope," is translated "regions" in Romans 15:23 RV; 2—Corinthians 11:10; Galatians 1:21 . See Part , A, No. 3.
King James Dictionary 
Region n. re'jun. L. regio, rego.
1. A tract of land or space of indefinite extent, usually a tract of considerable extent. It is sometimes nearly synonymous with country as all the region of Argob. Deuteronomy 3 .
He had dominion over all the region on this side the river. 1 Kings 4 .
So we speak of the airy region, the etherial regions, the upper regions, the lower regions.
2. The inhabitants of a region or district of country. Matthew 3 . 3. A part of the body as the region of the heart or liver. 4. Place rank.
He is of too high a region. Unusual.
Webster's Dictionary 
(1): ( n.) One of the grand districts or quarters into which any space or surface, as of the earth or the heavens, is conceived of as divided; hence, in general, a portion of space or territory of indefinite extent; country; province; district; tract.
(2): ( n.) Tract, part, or space, lying about and including anything; neighborhood; vicinity; sphere.
(3): ( n.) The upper air; the sky; the heavens.
(4): ( n.) The inhabitants of a district.
(5): ( n.) Place; rank; station.
International Standard Bible Encyclopedia 
rē´jun : A "district," as in modern English. The word "region" is used by English Versions of the Bible interchangeably with "country," "coasts," etc., for various Hebrew and Greek terms, but "region round about" is usually in the King James Version and invariably in the Revised Version (British and American) the translation of περίχωρος , perı́chōros , "surrounding country." For a possible technical use of "region" in Acts 16:6 and the Revised Version (British and American) Acts 18:23 . See Galatia .