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):

bulrush
    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]
    2: tall rush with soft erect or arching stems found in Eurasia,
       Australia, New Zealand, and common in North America [syn:
       bulrush, bullrush, common rush, soft rush, Juncus
       effusus]

Easton's 1897 Bible Dictionary:

Bulrush
   (1.) In Isa. 58:5 the rendering of a word which denotes
   "belonging to a marsh," from the nature of the soil in which it
   grows (Isa. 18:2). It was sometimes platted into ropes (Job.
   41:2; A.V., "hook," R.V., "rope," lit. "cord of rushes").

     (2.) In Ex. 2:3, Isa. 18:2 (R.V., "papyrus") this word is the
   translation of the Hebrew _gome_, which designates the plant as
   absorbing moisture. In Isa. 35:7 and Job 8:11 it is rendered
   "rush." This was the Egyptian papyrus (papyrus Nilotica). It was
   anciently very abundant in Egypt. The Egyptians made garments
   and shoes and various utensils of it. It was used for the
   construction of the ark of Moses (Ex. 2:3, 5). The root portions
   of the stem were used for food. The inside bark was cut into
   strips, which were sewed together and dried in the sun, forming
   the papyrus used for writing. It is no longer found in Egypt,
   but grows luxuriantly in Palestine, in the marshes of the Huleh,
   and in the swamps at the north end of the Lake of Gennesaret.
   (See CANE.)