The Collaborative International Dictionary of English v.0.48:
Invisible \In*vis"i*ble\, a. [F. invisible, L. invisibilis. See
In- not, and Visible.]
1. Incapable of being seen; not perceptible by vision; not
(a) Not visible due to an inherent property, such as lack
of color; as, the invisible air; invisible ink;
(b) hidden from view; out of sight;
(c) Not perceptible due to lack of light;
(d) Too small or too distant to be perceived; as, people
on the ground invisible at cruising altitude.
[1913 Webster +PJC]
To us invisible, or dimly seen
In these thy lowest works. --Milton.
2. Hidden from the public; as, invisible transactions.
3. imperceptible to the mind; as, differences invisible to
Invisible bird (Zool.), a small, shy singing bird
(Myadestes sibilons), of St. Vincent Islands.
Invisible green, a very dark shade of green, approaching to
black, and liable to be mistaken for it.