The Collaborative International Dictionary of English v.0.48:

Rummer \Rum"mer\, n. [D. roemer, romer, akin to G. r["o]mer, Sw.
   remmare; perhaps properly, Roman.]
   A large and tall glass, or drinking cup. [Obs.] --J. Philips.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rummer
    n 1: a large drinking glass (ovoid bowl on a stem) for drinking
         toasts