COMMON If someone or something is a thorn in your side or a thorn in the side, they continually annoy you or cause trouble for you. She has become a thorn in the side of the government since publishing a number of reports pointing out that public cash was being wasted. Note: You can also say that someone or something is a thorn in your flesh or a thorn in the flesh. Her mother is still a thorn in her flesh — demanding, complaining and weeping by turns. Note: This refers to a passage in the Bible, in which St Paul talks about an illness or other problem: `There was given to me a thorn in the flesh, the messenger of Satan to buffet me, lest I should be exalted above measure.' (2 Corinthians 12:7) Some Pharisees, who were strictly orthodox Jews, used to deliberately hurt themselves by putting thorns in their clothes to prick them when they walked.