I. ˈwȯk-ˌəp adjective
Date: circa 1919
1. : located above the ground floor in a building with no elevator
a walk-up apartment
2. : consisting of several stories and having no elevator
a walk-up tenement
3. : designed to allow pedestrians to be served without entering a building
the walk-up window of a bank
II. noun
Date: 1924
: an apartment or office building of several stories that has no elevator ; also : an apartment or office in such a building