invisible

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Impossible to see; not visible: Air is invisible.
2. adj. Not accessible to view; hidden: mountain peaks invisible in the fog.
3. adj. Not easily noticed or detected; inconspicuous: "The poor are politically invisible” ( Michael Harrington).
4. adj. Not published in financial statements: an invisible asset.
5. n. One that is invisible.

Century Dictionary and Cyclopedia

1. Not visible; incapable of being seen; imperceptible by the sight.
2. Out of sight; concealed or withdrawn from view: as, he keeps himself invisible.
3. n. A Rosicrucian: so called because of the secret character of the organization.
4. n. One who rejects or denies the visible character or external organization of the church; specifically [capitalized], a name given to certain German Protestants because they maintained that the church of Christ might be, and sometimes had been, invisible.

Wiktionary

1. adj. Unable to be seen; not visible.
2. adj. This template needs documentation and categorisation. Please create the documentation page.That is perfectly transparent, thus neither reflects nor absorbs light.
3. adj. That cannot be seen due to the lack of instruments, such as a microscope or telescope.
4. adj. That cannot be perceived by radar or other method of detection.
5. adj. Out of the field of vision of a person.
6. adj. Covered by another object.
7. adj. In the dark.
8. adj. That is perfectly camouflaged.
9. adj. That has undergone chroma keying or other technological means to not be seen on-screen.
10. adj. That is ignored by a person.
11. adj. That is apparently, but falsely, offline.

GNU Webster's 1913

1. adj. Incapable of being seen; not perceptible by vision; not visible.
2. adj. Not visible due to an inherent property, such as lack of color; .
3. adj. hidden from view; out of sight
4. adj. Not perceptible due to lack of light
5. adj. Too small or too distant to be perceived.
6. adj. Hidden from the public.
7. adj. imperceptible to the mind.
8. n. An invisible person or thing; specifically, God, the Supreme Being.
9. n. A Rosicrucian; -- so called because avoiding declaration of his craft.
10. n. One of those (as in the 16th century) who denied the visibility of the church.

WordNet 3.0

1. adj. not prominent or readily noticeable
2. adj. impossible or nearly impossible to see; imperceptible by the eye