| noun | the property of having two dimensions |
| noun | a want of animation or brilliance “the almost self-conscious flatness of Hemingway's style” |
| noun | a deficiency in flavor “it needed lemon juice to sharpen the flatness of the dried lentils” |
| noun | the property of having little or no contrast; lacking highlights or gloss |
| noun | inactivity; showing an unusual lack of energy “the general appearance of sluggishness alarmed his friends” |
| two-dimensional | adjective | involving two dimensions |
| flat | adjective | flattened laterally along the whole length (e.g., certain leafstalks or flatfishes) |
| plane | adjective | having a surface without slope, tilt in which no part is higher or lower than another |
| lusterless | adjective | lacking luster or shine |
| lustreless | adjective | lacking luster or shine |
| mat | verb | change texture so as to become matted and felt-like |
| matt | adjective | not reflecting light; not glossy |
| matte | adjective | not reflecting light; not glossy |
| languorous | adjective | lacking spirit or liveliness |
| lethargic | adjective | deficient in alertness or activity |
| sluggish | adjective | slow and apathetic |
| phlegmatic | adjective | showing little emotion |
| phlegmatical | adjective | showing little emotion |