flatness

Short definition from Wiktionary

Noun

1. 1
   The state of being flat
2. 2
   The state of being two-dimensional; planar : planarity
3. 3
   The state of being bland : dullness
4. 4
   Mattness, the quality of a painted surface which scatters or absorbs the light falling on it, so as to be substantially free from gloss or sheen
5. 5
   Lack of bouquet and freshness of a wine, through too much aeration or infection with film yeasts
6. 6
   slim-tailedness or platykurtosis.