flatness flatness /ˈflætnəs/

noun

1. () The property of having two dimensions  ( planeness , two-dimensionality , flatness )
   the property of having two dimensions
     The flatness of the surface made it ideal for painting.
   The flatness of the surface made it ideal for painting.
   
2. Inactivity; showing an unusual lack of energy  ( flatness , languor , lethargy , phlegm , sluggishness )
   inactivity; showing an unusual lack of energy
    The general appearance of sluggishness alarmed his friends
   the general appearance of sluggishness alarmed his friends
   
3. The property of having little or no contrast; lacking highlights or gloss  ( flatness , lusterlessness [ N. American] , lustrelessness [Canadian, British] , mat , matt , matte )
   the property of having little or no contrast; lacking highlights or gloss
   
4. A deficiency in flavor  ( flatness )
   a deficiency in flavor
    It needed lemon juice to sharpen the flatness of the dried lentils
   it needed lemon juice to sharpen the flatness of the dried lentils
   
5. A want of animation or brilliance  ( flatness )
   a want of animation or brilliance
    The almost self-conscious flatness of Hemingway's style
   the almost self-conscious flatness of Hemingway's style