accordion

A box-shaped musical instrument played by compressing or expanding its bellows while pressing its buttons or its keys, causing pallets to open, which allow air to flow across strips of brass or steel (reeds).

A disreputable accordion that had a leak somewhere and breathed louder than it squawked.

A vertical list of items that can be individually expanded and collapsed to reveal their contents.

Something, or set of things (concepts, etc), which can be expanded (or extended) and collapsed, like the musical instrument's pleated, folding bellows.

See also: telescoping

"Accordion" skirts are named from the musical instrument of that title, because the peculiar plaiting draws out and falls together again, in the same kind of folds, and with the same effect.

To fold up, in the manner of an accordion

I slit the wrapping with my pocketknife and the clothesline accordioned out in stiff loops.

Still in reverse, she goosed the gas and accordioned the running board a fraction of an inch more.