Word: underset
Part of speech: Noun
Syllables: un
der
set
Definition: undercurrent (of water)
Morphemes:
Affix: under-
Language: en
PoS: Prefix
Meaning: Under (in any sense): insufficient, insufficiently, below what is correct; subordinate to; beneath or behind.
Affix: set
Language: en
PoS: Noun
Meaning: A matching collection of similar things. (Note the similar meaning in Etymology 1, Noun.)