Visible vein
A blood vessel showing through the skin — the interior briefly visible at the surface.
A visible vein in a dream is the dream's image of the interior briefly showing at the surface. Veins under thin skin reveal what the body is carrying, and the visibility is not entirely voluntary. The dream brings the visible vein when something in your life — a feeling, a tiredness, a piece of family resemblance — has come close enough to the surface to be read from outside. A visible vein noted by a trusted person is the dream affirming the honest visibility. A visible vein noted by a stranger who should not have had that level of access is the dream noting that your interior has come too close to the surface and is being read in a context where you would have preferred to keep it private.