Wikipedia
The Cave of Adullam was originally a stronghold referred to in the Old Testament, near the town of Adullam, in which David, already anointed to succeed Saul as king, sought refuge from the latter. The word "cave" is usually used but "fortress", which has a similar appearance in writing, is used as well. Given that this was a bandits' hideout, it would be reasonable to describe this as a fortified cave. Wilhelm Gesenius' work Hebrew and Chaldee Lexicon to the Old Testament Scriptures translated into English by editor Samuel Prideaux Tregelles provides notes supporting Adullam to mean "a hiding place". Brown, Driver, and Briggs' Hebrew and English Lexicon of the Old Testament cite the Arabic word 'adula to mean "turn aside" and suggest Adullam to mean "retreat, refuge".
During this period, David passed up several opportunities to kill Saul, who in turn was attempting to kill his young rival, whose followers believed had been chosen by God to succeed King Saul. David refused to fight unfairly, for instance by killing the bellicose Saul in his sleep. According to the Old Testament, God honored David's high ethical standards and soon King David and his Mighty Men who had once hidden in the Cave of Adullam, were renowned throughout Israel for their deeds of valor.
The term "Cave of Adullam" has been used by political commentators referring to any small group remote from power but planning to return. Thus in Walter Scott's 1814 novel Waverley when the Jacobite rising of 1745 marches south through England, the Jacobite Baron of Bradwardine welcomes scanty recruits while remarking that they closely resemble David's followers at the Cave of Adullam; " videlicet, every one that was in distress, and every one that was in debt, and every one that was discontented".
The cave is the source of the term Adullamites, which is used generally to refer to groups of political outsiders plotting their comeback or the overthrow of the status quo, especially after recent defeat, and more specifically a short-lived anti-reform faction within the UK Liberal Party in 1866 under the leadership of Robert Lowe.
Usage examples of "cave of adullam".
Three of the thirty chief men went down to the rock to David at the cave of Adullam, when the army of Philistines was encamped in the valley of Reph’.
Now three of the thirty captains went down to the rock to David, into the cave of Adullam.
And three of the thirty chief went down, and came to David in the harvest time unto the cave of Adullam: and the troop of the Philistines pitched in the valley of Rephaim.
And three of the thirty chief men went down, and came about harvest time to David at the cave of Adullam, when a band of Philistines was encamped in the valley of Reph’.