subvisible

/sʌbˈvɪzəbəl/
adjective
  1. Too small or faint to be seen with the naked eye; not visible without magnification.
    • Air purifiers are designed to capture subvisible dust and allergens.
    • Subvisible cracks in the metal can lead to structural failure over time.
    • The water contained subvisible particles that could only be detected with a microscope.
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