a flag longer than it is wide (and often tapering)
"The baseball team raised their red pennant high above the stadium to celebrate winning the championship."
A flag normally used by naval vessels to represent a special condition.
"The captain raised a black pennant on the ship's mast to signal that they were carrying cargo for the king."
The broad pennant flown by commodores.
"The commodore raised his distinctive broad pennant to signal that he had assumed command of the fleet."