'Flag broom' definitions:

Definition of 'Flag broom'

From: GCIDE

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Flag broom, a coarse of broom, originally made of flags or rushes.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