crown of thorns is a noun meaning "any affliction that causes great suffering". It carries 3 recorded senses.
any affliction that causes great suffering
“that is his cross to bear”
“he bears his afflictions like a crown of thorns”
somewhat climbing bushy spurge of Madagascar having long woody spiny stems with few leaves and flowers with scarlet bracts
a mock crown made of thorn branches that Roman soldiers placed on Jesus before the Crucifixion
Definitions, synonyms and semantic relations for crown of thorns come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.