Source : WordNet®

crown of thorns
     n 1: any affliction that causes great suffering; "that is his
          cross to bear"; "he bears his afflictions like a crown
          of thorns" [syn: {cross}]
     2: somewhat climbing bushy spurge of Madagascar having long
        woody spiny stems with few leaves and flowers with scarlet
        bracts [syn: {Christ thorn}, {Christ plant}, {Euphorbia
        milii}]
     3: a mock crown made of thorn branches that Roman soldiers
        placed on Jesus before the Crucifixion