Glossary Term Definition
A vertical stress axis in letterforms, characteristic of Neoclassical and Romantic typefaces where the thinnest parts of round strokes are at top and bottom.
Definition
A vertical stress axis in letterforms, characteristic of Neoclassical and Romantic typefaces. In a rationalist axis, the thinnest parts of round strokes are at top and bottom (12 o'clock and 6 o'clock), reflecting a geometrically constructed rather than calligraphically derived form. Contrast with the humanist axis, which is oblique.
Source
No access — Robert Bringhurst — p. 328:
A vertical stress axis in letterforms.