Easton's Bible Dictionary (1897)
Used to support a building (Judg. 16:26, 29); as a trophy or memorial (Gen. 28:18; 35:20; Ex. 24:4; 1 Sam. 15:12, A.V., “place,” more correctly “monument,” or “trophy of victory,” as in 2 Sam. 18:18); of fire, by which the Divine Presence was manifested (Ex. 13:2). The “plain of the pillar” in Judg. 9:6 ought to be, as in the Revised Version, the “oak of the pillar”, i.e., of the monument or stone set up by Joshua (24:26).
Smith's Bible Dictionary (1863)
The notion of a pillar is of a shaft or isolated pile either supporting or not supporting a roof. But perhaps the earliest application of the pillar was the votive or monumental, This in early times consisted of nothing but a single stone or pile of stones. (Genesis 28:18; 31:40) etc. The stone Ezel, (1 Samuel 20:19) was probably a terminal stone or a way-mark. The “place” set up by Saul (1 Samuel 15:12) is explained by St, Jerome to be a
trophy. So also Jacob set up a pillar over Rachel’s grave. (Genesis 36:20) The monolithic tombs and obelisks of Petra are instances of similar usage. Lastly, the figurative use of the term “pillar,” in reference to the cloud and fire accompanying the Israelites on their march or as in (Song of Solomon 3:6) and Reve 10:1 Is plainly derived from the notion of an isolated column not supporting a roof.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
PIL'LAR. This word is often used metaphorically in the Bible, thus a pillar of fire, cloud, smoke, etc., denoting a fire, a cloud, or a mass of smoke in the form of a pillar. Ex 13:21; Jud 20:40. Besides, in architecture, where it was employed both as support and ornament, it was common to erect a pillar as a monument of some distinguished person or event. Gen 28:18; Gen 35:20; Josh 24:26. "The plain of the pillar," Jud 9:6, properly the "oak of
the pillar," a tree near Shechem under which Abimelech was crowned.