Lack of transparency
Else clues• Dullness
• Lack of clarity
• Light-blocking ability
• Lucidity's opposite
• Milk quality
• Milk-glass property
• Murkiness
• Murky quality
• Obscurity
• The phenomenon of not permitting the passage of electromagnetic radiation
• Incomprehensibility resulting from obscurity of meaning
• The quality of being opaque to a degree
• The degree to which something reduces the passage of light