Strictly female attire in Western fashion, a dress is basically a large shirt or
tunic with the waist or the entire upper half of the
garment half-fitted or fitted while the lower half can be
loose or tight (which inhibits the ability to walk).
The lower half, or skirt, ranges in length from above the knees to the floor.
"Skirt" comes from "skyrta", an old Norse word for "shirt", so it seems appropriate to call an entire dress a skirt and not just the lower half.
Skirt is also slang for a woman, often one who is morally loose.
The skirt was once practically a gender-neutral
garment before the Rennaissance; men and women wore
togas and tunics and nobody said anything about it, and leggings were worn beneath for warmth. Now skirts are limited to women, unless you count the
kilt, which looks absolutely stunning!