What is the meaning of Shadow?

A dark image projected onto a surface where light (or other radiation) is blocked by the shade of an object.

Relative darkness, especially as caused by the interruption of light; gloom; obscurity.

An area protected by an obstacle (likened to an object blocking out sunlight).

A reflected image, as in a mirror or in water.

That which looms as though a shadow.

A small degree; a shade.

An imperfect and faint representation.

A trainee, assigned to work with an experienced officer.

One who secretly or furtively follows another.

An inseparable companion.

A drop shadow effect applied to lettering in word processors etc.

An influence, especially a pervasive or a negative one.

A spirit; a ghost; a shade.

An uninvited guest accompanying one who was invited.

An unconscious aspect of the personality.

Unofficial, informal, unauthorized, but acting as though it were.

Having power or influence, but not widely known or recognized.

Acting in a leadership role before being formally recognized.

Part of, or related to, the opposition in government.

To shade, cloud, or darken.

To block light or radio transmission from.

To secretly or discreetly track or follow another, to keep under surveillance.

To represent faintly and imperfectly.

To hide; to conceal.

To accompany (a professional) during the working day, so as to learn about an occupation one intends to take up.

To make (an identifier, usually a variable) inaccessible by declaring another of the same name within the scope of the first.

To apply the shadowing process to (the contents of ROM).

Source: wiktionary.org