Dress & Attire

Meaning of transparent clothing

Q: Can you please tell me how do we determine if a dress is transparent or not. Most of my dresses are such that if I hold them in front of my eyes, I can see whatever is on the other side. But if I put my hand below the dress or wear the dress, my body colour cannot be seen. Are these dresses considered to be transparent? What is the way of determining if a dress is transparent or not?