single-decker
US /ˌsɪŋ.ɡəlˈdek.ɚ/
UK /ˌsɪŋ.ɡəlˈdek.ɚ/

1.
a bus that has only one level for passengers
:
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The school trip used a single-decker bus.
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Most city routes are served by single-deckers.
1.
having only one level or deck
:
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We booked a single-decker boat for the river tour.
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The new exhibition hall is a spacious single-decker structure.