Boyd’s Bible Dictionary:

(highlanders). One of the nations of Canaan before the Hebrew conquest (Gen. 10:16; 14:7; Num. 13:29; Deut. 1:20; Josh. 5:1; 10:6; 11:3; 1 Sam. 23:29). Occupied both sides of the Jordan (Josh. 13:15-27; Num. 21:21).

Concise Bible Dictionary:

A people descended from Canaan, son of Ham (Gen. 10:16). They dwelt in the mountains, as their name signifies, and were apparently at times in the mountains both east and west of the Jordan (Num. 13:29; Josh. 5:1; Judg. 1:34-36; Judg. 10:8; 1 Kings 4:19). Being the most dominant and the most corrupt people or tribe they sometimes represent the Canaanites generally (Gen. 15:16; 1 Kings 21:26). When Abraham was at Hebron some confederated with him (Gen. 14:13). A remnant out of the Gentile nations was thus associated with the heir of promise, though Lot (a type of Israel after the flesh) had separated from him.
When Israel approached the promised land, they were in the east, and refused to let Israel pass; but they were overcome, their cities taken, and the people slain, with Sihon their king (Num. 21:21-26; Deut. 2:24; Amos 2:9-10). Some must have escaped, for we read of them later, and one of the controversies Jehovah had with Israel was for worshipping their gods (Ezra 9:1-2). Solomon made them tributary. (1 Kings 9:20-21; 2 Chron. 8:7-8). The Gibeonites were a remnant of the Amorites (2 Sam. 21:2). After this nothing is heard of them. The low state of Jerusalem (Judah) by nature is described by stating her origin, her father being an Amorite and her mother a Hittite, but God in grace had compassion upon her in her degradation, and raised her into great glory; though, alas, she was shamefully unfaithful (Ezek. 16:3-43.

Strong’s Dictionary of Hebrew Words:

probably a patronymic from an unused name derived from 559 in the sense of publicity, i.e. prominence; thus, a mountaineer; an Emorite, one of the Canaanitish tribes
KJV Usage:

Jackson’s Dictionary of Scripture Proper Names:

a sayer

Potts’ Bible Proper Names:

A bitter people; dwellers on the summits:―a Canaanitish tribe, Deut. 20:17. {Populus amarus}