A mock crown, made from thorn branches, that Roman soldiers put on the head of Jesus before the Crucifixion. The soldiers also “bowed the knee before him, and mocked him, saying, ‘Hail, King of the Jews!’”
Note: In common usage, a “crown of thorns” may be anything that causes intense suffering: “The jailed political leader bears her afflictions like a crown of thorns.” Similar to the expression “cross to bear.” (See Crucifixion.)