Circular straw hat with a flat top and straight brim. The crown is trimmed with a band of ribbon. Boaters are so named because, teamed with striped blazers and flannel trousers, they made up the male uniform for the summer sport of boating from the late 19th century until about 1940.
A boater is a flat-topped hat with a relatively narrow flat brim. It was traditionally, made of stiffened straw braid, but synthetic fibers are now sometimes used.
a straw hat to cover dumb heads