Word: twinset
Part of speech: Noun
Syllables: twin
set
Definition: A pair of cars or locomotives that are permanently coupled and treated as a single unit.
Morphemes:
Affix: twin
Language: en
PoS: Noun
Meaning: Either of two similar or closely related objects, entities etc.
Affix: set
Language: en
PoS: Noun
Meaning: A matching collection of similar things. (Note the similar meaning in Etymology 1, Noun.)