Definify.com

Webster 1828 Edition

metonymic ‎(comparative more metonymic, superlative most metonymic)

Of, or relating to, a word or phrase that names an object from a single characteristic of it or of a closely related object.
The British government is often referred to by the metonymic expression "Downing Street".
- 1999, Udo Hahn & Katja Markert, "On the Formal Distinction between Literal and Figurative Language", Progress in Artificial Intelligence: 9th Portuguese Conference on Artificial Intelligence, page 140
  With a metonymic expression encountered in almost every sixth utterance, an uncontroversial need for dealing with this problem is demonstrated.

Of, or relating to, a word that names an object from a single characteristic of it or of a closely related object

metonymic ‎(plural metonymics)

metonym — see metonym