Glossary Term Definition
Two types of serif attachment: abrupt serifs break suddenly from the stem at an angle, while adnate serifs flow smoothly into or out of the stem (historically described as bracketed).
Definition
Serifs are either abrupt — meaning they break from the stem suddenly at an angle — or they are adnate, meaning that they flow smoothly into or out of the stem. In the older typographic literature, adnate serifs are generally described as bracketed.
Source
No access — Robert Bringhurst — p. 321:
Serifs are either abrupt — meaning they break from the stem suddenly at an angle — or they are adnate, meaning that they flow smoothly into or out of the stem.