Boyd’s Bible Dictionary:
A word of frequent occurrence in Psalms, and supposed to mean an interlude in vocal music, or a pianissimo of all parts
(Psa. 9:16; Hab. 3:3,9,13).
“Selah” From Concise Bible Dictionary:
A term occurring in Habakkuk 3:3, 9, 13, and many times in the Psalms. There have been various suggestions as to its meaning, but its signification is not really known. The Targum mostly renders the word “forever.” The LXX has διάψαλμα, denoting, as some think, “a pause, a break or rest.” “Pause, consider,” is perhaps its signification.
“Sela, Selah” From Concise Bible Dictionary:
The rock city of Edom (2 Kings 14:7; Isa. 16:1). The same Hebrew word is that usually translated “rock.” The place was taken by Amaziah, who called it JOKTHEEL. It is judged to be the same as PETRA (which occurs in the margin of Isaiah 16:1). Petra is a remarkable place. Though about two thousand feet above the sea, it is shut in by mountain-cliffs, and is entered by a narrow ravine, through which also the river winds. The tombs cut in the rocks are large, especially one called el Khuzneh, which has three rows of columns. The tiers of a theater remain, a triumphal arch, and ruined bridges. There is a sort of awe-inspiring grandeur in the place. The Bedouins are very troublesome, and jealous of visitors entering, supposing they come to search for treasure. Some have with difficulty escaped with their lives after being well fleeced. Petra lies 30° 22' N, 35° 43' E.
Strong’s Dictionary of Hebrew Words:
Meaning:
from 5541; suspension (of music), i.e. pause
Jackson’s Dictionary of Scripture Proper Names:
a rock: crag (2 Kings 14:7) : make prominent
Potts’ Bible Proper Names:
To pause; to rest; elevation; loud; clear:―occurs frequently in Psalms, Psa. 9:16. {Distinctio}