There are two Hebrew words rendered "flag" in our Bible:

+ A word of Egyptian origin, and denoting "any green and course herbage, such as rushes and reeds, which grows in marshy places." (Genesis 41:2,18) (here translated meadow). It is perhaps the Cyperus esculentus .

+ A word which appears to be used in a very wide sense to denote "weeds of any kind." (Exodus 2:3,5; Isaiah 19:6)