The Collaborative International Dictionary of English v.0.48:

Reed-mace \Reed"-mace`\ (r[=e]d"m[=a]s`), n. (Bot.)
   The cat-tail.
   [1913 Webster]

WordNet (r) 3.0 (2006):

reedmace
    n 1: tall marsh plant with cylindrical seed heads that explode
         when mature shedding large quantities of down; its long
         flat leaves are used for making mats and chair seats; of
         North America, Europe, Asia and North Africa [syn:
         cat's-tail, bullrush, bulrush, nailrod, reed
         mace, reedmace, Typha latifolia]