1. Not transparent to X-rays or other forms of radiation
   - radiopaque

Encyclopedia: Radio-opaque

• unperformed
• unpermed
• unpermissive
• unpermissiveness
• unperplexed
• unperson
• unpersuadable
• unpersuaded
• unpersuasive
• unpersuasiveness
• unperturbed
• unpick
• unpictured
• unpicturesque
• unpierced
• unpigmented
• unpillared
• unpin
• unpitying
• unplaced
• unplanned
• unplanted
• unplastered
• unplayable
• unplayful