The Collaborative International Dictionary of English v.0.48:

Flag \Flag\, n. [From Flag to hang loose, to bend down.]
   (Bot.)
   An aquatic plant, with long, ensiform leaves, belonging to
   either of the genera Iris and Acorus.
   [1913 Webster]

   Cooper's flag, the cat-tail (Typha latifolia), the long
      leaves of which are placed between the staves of barrels
      to make the latter water-tight.

   Corn flag. See under 2d Corn.

   Flag broom, a coarse of broom, originally made of flags or
      rushes.

   Flag root, the root of the sweet flag.

   Sweet flag. See Calamus, n., 2.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Water torch \Wa"ter torch`\ (Bot.)
   The common cat-tail (Typha latifolia), the spike of which
   makes a good torch soaked in oil. --Dr. Prior.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bulrush \Bul"rush`\ (b[.u]l"r[u^]sh`), n. [OE. bulrysche,
   bolroysche; of uncertain origin, perh. fr. bole stem + rush.]
   (Bot.)
   A kind of large rush, growing in wet land or in water.
   [1913 Webster]

   Note: The name bulrush is applied in England especially to
         the cat-tail (Typha latifolia and Typha
         angustifolia) and to the lake club-rush (Scirpus
         lacustris); in America, to the Juncus effusus, and
         also to species of Scirpus or club-rush.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

cattail \cat"tail\, Cat-tail \Cat"-tail\(k[a^]t"t[=a]l), n.
   (Bot.)
   A tall erect rush or flag (Typha latifolia) growing widely
   in fresh and salt marshes, with long, flat, sword-shaped
   leaves, having clusters of small brown flowers in a dense
   cylindrical spike at the top of the stem; -- called also
   bulrush and reed mace. The leaves are frequently used for
   seating chairs, making mats, etc. See Catkin.
   [1913 Webster + WordNet 1.5]

   Note: The lesser cat-tail is Typha angustifolia.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Typha latifolia
    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]