Roget's Thesaurus: Entry 251 (Flatness)

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#251. Flatness. -- N. flatness &c. adj.; smoothness &c. 255.

plane; level &c. 213; plate, platter, table, tablet, slab.

V. render flat, flatten; level &c. 213.

Adj. flat, plane, even, flush, scutiform[obs], discoid; level &c. (horizontal) 213; flat as a pancake, flat as a fluke, flat as a flounder, flat as a board, flat as my hand.