vein

• vein
• 1 [countable] one of the tubes which carries blood to your heart from other parts of your body [↪ artery]:
• the pulmonary vein
• She felt the blood racing through her veins as they kissed.
• 2 [countable] one of the thin lines on a leaf or on an insect's wing
• 3 [countable] one of the thin lines on a piece of cheese or some types of stone
• 4 [countable] a thin layer of a valuable metal or mineral which is contained in rock
• vein of
• veins of gold
• 5

   in a ... vein

  in a particular style of speaking or writing about something
• in the same vein/in a similar vein
• There was more humour, in much the same vein.
• in a serious/light-hearted etc vein
• poems in a lighter vein
• 6

   a vein of humour/malice etc

  a small amount of humour etc:
• In voicing our fear of old age, Rivers has discovered a rich vein ofcomedy.
• ➔ deep vein thrombosis, varicose veins

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.