Telangiectasia in Plain Terms

Telangiectasia is a long word that can stop a reader mid-line. Start with its definition.
The definition as printed
my.clevelandclinic.org states:
Telangiectasia is the medical term for a small, dilated (widened) blood vessel that can form just beneath the surface of your skin or mucous membranes.
The source page is spider vein causes, symptoms and treatment.
What each phrase asks of you
"Medical term" means the word is a label. You do not need to use it. "Dilated (widened)" tells you to read dilated as widened. "Just beneath the surface" tells you the vessel sits close to the surface of your skin or mucous membranes.
One word on the same paperwork
Another term you may meet nearby is varicose veins. The varicose veins entry in the MedlinePlus encyclopedia is a separate page on that term.
Saying it your way
If a document uses the word, you can say "small, widened blood vessel" to your provider instead. If you hear the word at a visit, ask your provider to point out the vessel.
Boiled down to one directive
Directive, per my.clevelandclinic.org: telangiectasia means a small, widened blood vessel near the surface of the skin or mucous membranes. A vein treatment name you may meet nearby is covered in sclerotherapy treatment and recovery.