mud midget vs duckweed

mud midget and duckweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
mud midget	Yes	No	No	No
duckweed	Yes	No	No	No

As nouns, duckweed is a hypernym of mud midget; that is, duckweed is a word with a broader meaning than mud midget:

mud midget: having narrow flat sickle-shaped submerged fronds; North America
duckweed: any small or minute aquatic plant of the family Lemnaceae that float on or near the surface of shallow ponds

mud midget (noun)	duckweed (noun)
having narrow flat sickle-shaped submerged fronds; North America	any small or minute aquatic plant of the family Lemnaceae that float on or near the surface of shallow ponds