COMB in ADJ [ADJ n](用于 double, single 等形容词后)表示“…层的”-decker is used after adjectives like 'double' and 'single' to indicate how many levels or layers something has. (用于 double, single 等形容词后)表示“…层的”
...a red double-decker bus full of tourists.
载满了游客的红色双层巴士
...a triple-decker peanut butter and jelly sandwich.