Definition
Slice
To slice a solid is to pass a flat plane through it and reveal a cross-section.
What it means
Picture a perfectly flat sheet moving through a solid shape. Only the place where the sheet and the solid meet counts as the slice. That meeting shape is flat, and it can change when the sheet moves or tilts.
Remember it
A flat sheet passes through a solid and leaves one flat meeting shape.
Example
Pass a plane through the middle of a cube, parallel to one face. The cross-section is a square the same size as that face.
Watch for
A drawing of one outside face is not automatically a slice; a slice names where a plane meets the solid.
Common mix-up
The slice is flat even though the original object is three-dimensional.
Exact meaning
To slice a solid in geometry is to intersect it with a plane. The two-dimensional figure where the plane meets the three-dimensional solid is the cross-section.