The Collaborative International Dictionary of English v.0.48:
Metonymic \Met`o*nym"ic\, Metonymical \Met`o*nym"ic*al\, a. [See Metonymy.] Used by way of metonymy; using the name of one thing for that of another with which it is closely associated. -- Met`o*nym"ic*al*ly, adv. [1913 Webster]WordNet (r) 3.0 (2006):
metonymically adv 1: in a metonymic manner