the human eye, unassisted by optics, such as a telescope, microscope, or spectacles. (*Typically: appear to ~; look to ~; see with ~; visible to~.) I can't see the bird's markings with the naked eye.The scientist could see nothing in the liquid with the naked eye, but with the aid of a microscope, she identified the bacteria.That's how it appears to the naked eye.
Sight unassisted by an instrument such as a microscope or telescope. For example, These insects are too small to be seen with the naked eye. This expression was first recorded in 1664.