thread vein 
noun
A very slender vein, especially one on the face that is visible through the skin.I can remember having a small thread vein that looked a bit like a blue map under the skin....
- Telangiectasia are also referred to as spider veins, star bursts, thread veins, or matted veins.
- Small patches of brown skin discolouration or areas of thread veins form where the veins were removed.
- untouchability
- untouchable
- untouchableness
- untouched
- untouristed
- untoward
- untowardly
- untowardness
- untraceable
- untraceably
- untraced
- untracked
- untraditional
- untrainable
- untrained
- untrammeled
- untrammelled
- untransferable
- untransformed
- untranslatability
- untranslatable
- untranslatably
- untranslated
- untraveled
- untravelled