unseeable -
impossible or nearly impossible to see; imperceptible by the eye; "the invisible man"; "invisible rays"; "an invisible hinge"; "invisible mending"
seeable,
visible present and easily available; "the cash on hand is adequate for current needs"; "emergency police were on hand in case of trouble"; "a visible supply"; "visible resources"
imperceptible,
unperceivable impossible or difficult to perceive by the mind or senses; "an imperceptible drop in temperature"; "an imperceptible nod"; "color is unperceivable to the touch"
covert secret or hidden; not openly practiced or engaged in or shown or avowed; "covert actions by the CIA"; "covert funding for the rebels"
camouflaged made invisible by means of protective coloring
out of sight,
concealed,
hidden hidden on any grounds for any motive; "a concealed weapon"; "a concealed compartment in his briefcase"
infrared having or employing wavelengths longer than light but shorter than radio waves; lying outside the visible spectrum at its red end; "infrared radiation"; "infrared photography"
lightless without illumination; "came up the lightless stairs"; "the unilluminated side of Mars"; "through dark unlighted (or unlit) streets"
nonvisual not resulting in vision; "nonvisual stimuli"
occult hidden and difficult to see; "an occult fracture"; "occult blood in the stool"
ultraviolet having or employing wavelengths shorter than light but longer than X-rays; lying outside the visible spectrum at its violet end; "ultraviolet radiation"; "an ultraviolet lamp"
