monochrome

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A picture, especially a painting, done in different shades of a single color.
• noun The art or technique of executing such a picture.
• noun The state of being in a single color.
• noun A black-and-white image, as in photography or on television.

from The Century Dictionary.

• Of one color; painted in one color; monochromic.
• noun Painting or a painting in one color, which may, however, be relieved by the use of lighter and darker shades. Compare camaïeu and grisaille.

from the GNU version of the Collaborative International Dictionary of English.

• noun A painting or drawing in a single color; a picture made with a single color.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A black and white image, especially such a photograph.
• noun dated A painting executed in shades of a single colour.
• noun A ceramic glaze of a single colour; an object so glazed.
• adjective having only one colour
• adjective photography representing colours with shades of gray

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun painting done in a range of tones of a single color
• noun a black-and-white photograph or slide
• adjective having or appearing to have only one color