Easton's Bible Dictionary (1897)
(1.) Heb. gib’eah, a curved or rounded hill, such as are common to Palestine (Ps. 65:12; 72:3; 114:4, 6). (2.) Heb. har, properly a mountain range rather than an individual eminence (Ex. 24:4, 12, 13, 18; Num. 14:40, 44, 45). In Deut. 1:7, Josh. 9:1; 10:40; 11:16, it denotes the elevated district of Judah, Benjamin, and Ephraim, which forms the watershed between the Mediterranean and the Dead Sea. (3.) Heb. ma’aleh in 1 Sam. 9:11. Authorized
Version “hill” is correctly rendered in the Revised Version “ascent.” (4.) In Luke 9:37 the “hill” is the Mount of Transfiguration.
Schaff's Bible Dictionary
HILL, HILLS. There is some confusion in the use of "hill" and "mountain" in the A.V. Thus the "hill country" of Luke 1:39 is the "mountain of Judah," Josh 20:7. Again, precisely the same elevation is called both mountain and hill, Luke 9:28; cf. 1 Chr 9:37. But the original text is exact, employing words of quite different meaning to express the different elevations of hills and mountains. See Palestine, Mountain.