HEPTAGONAL a.
Having seven angles or sides. Heptagonal numbers (Arith.), the numbers of the series 1, 7, 18, 34, 55, etc., being figurate numbers formed by adding successively the terms of the arithmetical series 1, 6, 11, 16, 21, etc.
INTAGLIO n.
A cutting or engraving; a figure cut into something, as a gem, so as to make a design depressed below the surface of the material; hence, anything so carved or impressed, as a gem, matrix, etc.; -- opposed to cameo. Also used adjectively.