means A digital (or originally paper) grid of rows and columns used to organize, calculate, and analyze data, where changing one cell can ripple through formulas across the whole sheet.

from A plain compound of "spread" and "sheet" — the word originally named an accountant's large sheet of paper "spread" open across two facing pages of a ledger, so numbers could march in rows and columns. When the software VisiCalc arrived in the late 1970s, it borrowed the old bookkeeper's term for its glowing electronic grid, and the name stuck.