Glossary Term Definition
A serif that extends on both sides of the stem, as opposed to a unilateral or reflexive serif which extends mainly in one direction.
Definition
A bilateral serif extends to both sides of the stem. Most serifed roman letters have bilateral foot serifs and bilateral head serifs, but the serifs on the ascender of d and on the descender of p are normally unilateral or reflexive.
Source
No access — Robert Bringhurst — p. 322:
A bilateral serif extends to both sides of the stem.