Dictionary of Biblical Words:
This occurs in Heb. 12:22, where it is put in contrast with Mount Sinai, the one being descriptive of law, and the other of heavenly grace and blessing. In Gal. 4, a similar figure is used, only the words are not the same.
Concise Bible Dictionary:
The ordinary word for this is har, which is employed both for the mountain ranges, some of which run through Israel from north to south, and also for the higher mountains that rise upon those ranges or on the plains. Thus in 2 Chronicles 13:4 it says, “Mount Zemaraim, which is in mount Ephraim,” which means that mount Zemaraim was situated in the hill-country of Ephraim. Mount Ephraim does not refer to any particular mountain; but to the range of hills, or hill country in Ephraim, extending from Bethel to the plains of Jezreel. In like manner there are parts that can be called hill-country throughout all the land, as in Joshua 13:6 and Luke 1:39,65. Each of the mountains is considered under its own name.
Strong’s Dictionary of Greek Words:
Meaning:
probably from an obsolete ὄρω (to rise or "rear"; perhaps akin to 142; compare 3733); a mountain (as lifting itself above the plain)
KJV Usage:
hill, mount(-ain)