staircase

Short definition from Wiktionary

Noun

1. 1
   A flight of stairs; a stairway.
2. 2
   A connected set of flights of stairs; a stairwell.
3. 3
   A set of locks (enclosed sections of waterway) mounted one above the next.

Verb

1. 1
   To modify (a signal, a graph, etc.) to reduce a smooth curve to a series of discrete steps.
2. 2
   To increase one's share in a co-ownership.