The Collaborative International Dictionary of English v.0.48:
cattail \cat"tail\, Cat-tail \Cat"-tail\(k[a^]t"t[=a]l), n.
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.