'Thorn in the flesh' definitions:

Definition of 'Thorn in the flesh'

From: Easton

Thorn in the flesh (2 Cor. 12:7-10). Many interpretations have been given of this passage.
Roman Catholic writers think that it denotes suggestions to impiety.
Luther, Calvin, and other Reformers interpret the expression as denoting temptation to unbelief.
Others suppose the expression refers to "a pain in the ear or head," epileptic fits, or, in general, to some severe physical infirmity, which was a hindrance to the apostle in his work (comp. 1 Cor. 2:3; 2 Cor. 10:10; 11:30; Gal. 4:13, 14; 6:17). With a great amount of probability, it has been alleged that his malady was defect of sight, consequent on the dazzling light which shone around him at his conversion, acute opthalmia. This would account for the statements in Gal. 4:14; 2 Cor. 10:10; also Acts 23:5, and for his generally making use of the help of an amanuensis (comp. Rom. 16:22, etc.).
Another view which has been maintained is that this "thorn" consisted in an infirmity of temper, to which he occasionally gave way, and which interfered with his success (comp. Acts 15:39; 23:2-5). If we consider the fact, "which the experience of God's saints in all ages has conclusively established, of the difficulty of subduing an infirmity of temper, as well as the pain, remorse, and humiliation such an infirmity is wont to cause to those who groan under it, we may be inclined to believe that not the least probable hypothesis concerning the 'thorn' or 'stake' in the flesh is that the loving heart of the apostle bewailed as his sorest trial the misfortune that, by impatience in word, he had often wounded those for whom he would willingly have given his life" (Lias's Second Cor., Introd.).