spill range
the block of cells a multi-value formula writes its results into.
A formula that returns several values writes them into neighbouring cells. That block is the spill range, and only the top-left cell holds the formula — the rest are outputs that disappear if the formula is deleted.
The spill range must be empty. Anything in the way — data, a merged cell, the edge of the grid — blocks the whole formula and produces #SPILL!.
The spill range resizes itself as the source data grows or shrinks, which is what makes dynamic arrays useful for lists whose length changes.