To say what a thing is like. Description reports and does not instruct — reading one as an instruction is a common error.
Latin describere (to write down, sketch, copy), from de- (down) + scribere (to write); to say what a thing is like, reporting its shape rather than instructing what should be done about it.
The Latin root is a copy made by writing something down, not an order given — describere records a shape, it does not command one. Treating a description as a set of steps mistakes a report for a recipe.