The Greek word ba·sa·niʹzo (and related terms) occurs over 20 times in the Christian Greek Scriptures. It basically meant “test by the proving stone [baʹsa·nos]” and, by extension, “examine or question by applying torture.” Lexicographers point out that in the Christian Greek Scriptures it is used with the sense of ‘vexing with grievous pains; being harassed, distressed.’
The Bible used ba·sa·niʹzo in a number of instances. For example, a manservant afflicted with paralysis was “terribly tormented” (NW) or “racked with pain” (NE) by it. (Mt 8:6; compare 4:24.) Also, Lot “used to torment his soul” (Ro) or “was vexed” (Mo, RS) by the lawless deeds of the people of Sodom. (2Pe 2:8) The word is even used in regard to the difficult progress of a boat.
The Greek noun ba·sa·ni·stesʹ occurring at Matthew 18:34 is rendered “jailers” in some translations (AT, Fn, NW; compare Mt 18:30) and “tormentors” or “torturers” in others. (AS, KJ, JB) Torture was sometimes used in prisons to obtain information (compare Ac 22:24, 29, which shows that this was done, although ba·sa·niʹzo is not used here), so ba·sa·ni·stesʹ came to be applied to jailers. Regarding its use at Matthew 18:34, The International Standard Bible Encyclopaedia observed: “Probably the imprisonment itself was regarded as ‘torment’ (as it doubtless was), and the ‘tormentors’ need mean nothing more than jailers.” (Edited by J. Orr, 1960, Vol. V, p. 2999) Thus, the mentioning in Revelation 20:10 of ones who will be “tormented day and night forever and ever” evidently indicates that they will be in a condition of restraint. That a condition of restraint can be spoken of as “torment” is indicated by the parallel accounts at Matthew 8:29 and Luke 8:31.
Some commentators have pointed to Biblical instances of the word “torment” to support the teaching of eternal suffering in fire. However, as just indicated, there is Scriptural reason to believe that Revelation 20:10 does not have that sense. In fact, verse 14 shows that “the lake of fire” in which the torment occurs, actually means “the second death.” And though Jesus spoke of a certain rich man as “existing in torments” (Lu 16:23, 28), as the article LAZARUS (No. 2) shows, Jesus was not describing the literal experience of a real person but, rather, was setting forth an illustration. Revelation provides a number of other instances where “torment” clearly has an illustrative or symbolic sense, as is evident from context.