Definition

/ˈʃædəʊ/

noun

A dark image projected onto a surface where light (or other radiation) is blocked by the shade of an object.
“My shadow lengthened as the sun began to set.”
Relative darkness, especially as caused by the interruption of light; gloom, obscurity.
“I immediately jumped into shadow as I saw them approach.”
A area protected by an obstacle (likened to an object blocking out sunlight).
“The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them.”
A reflected image, as in a mirror or in water.
That which looms as though a shadow.
“I don't have a shadow of doubt in my mind that my plan will succeed. The shadow of fear of my being outed always affects how I live my life. I lived in her shadow my whole life.”

verb

To shade, cloud or darken.
“The artist chose to shadow this corner of the painting.”
To block light or radio transmission from.
“Looks like that cloud's going to shadow us.”
To secretly or discreetly track or follow another, to keep under surveillance.
To represent faintly and imperfectly.
To hide; to conceal.

adjective

Unofficial, informal, unauthorized, but acting as though it were.
“The human resources department has a shadow information technology group without headquarters knowledge.”
Having power or influence, but not widely known or recognized.
“The director has been giving shadow leadership to the other group's project to ensure its success.”
Acting in a leadership role before being formally recognized.
“The insurgents’ shadow government is being crippled by the federal military strikes.”
Part of, or related to, the opposition in government.