spider vein       
noun [ C usually plural ] uk/ˈspaɪ.də ˌvəɪn/ us/ˈspaɪ.dɚ ˌvəɪn/ (also UK thread vein)
 蛛状曲张静脉
a very thin vein (= tube that carries blood) that can be seen on the legs or face
  She consulted a dermatologist about some unsightly spider veins on her legs. 她腿上有一些难看的蛛状曲张静脉,因此咨询了皮肤科医生。 
 Spider veins are not a medical condition. 蛛状曲张静脉并不是一种病症。 
 - More examples
 - Spider veins can form at puberty and can worsen with age.
 - It's almost impossible to eliminate every last spider vein.
 - The company sells a specialized needle for removing spider veins.