IPA: /sʌbˈvɪʒ.əl/
KK: /sʌbˈvɪʒ.əl/
Referring to something that is too faint or dim to be seen without assistance.
The subvisual details of the painting were only visible under special lighting.
Subvisual → It is formed from "sub-" (meaning under or below) and "visual" (from Latin "visus", meaning sight). The word "subvisual" refers to something that is below the threshold of sight or not visible to the naked eye.
Think of something that is 'under' ('sub-') what you can 'see' ('visual') — that's why subvisual means something that cannot be seen.