Falling is among the most commonly reported dream images, across cultures and ages. The dream usually ends before you land, often with a jolt.
That jolt has a name: a hypnic jerk, or sleep start. It is a brief muscle twitch some people notice while dropping off, and it is widely described as harmless. Whether it is linked to the feeling of falling is not settled, so be cautious about any tidy explanation.
As an image, falling is read in several ways. Some link it to a sense of losing control or support, others to letting go. A fall from a height (falling down stairs is a close cousin) often comes with the feeling that something has slipped away.
Questions that help: what was under you before you fell, were you pushed or did you slip, and did you want to land? Your answers say more than any list of meanings.
For background on sleep starts, see the overview of the hypnic jerk.
This guide is general information, not medical advice. If dreams or sleep are affecting your health, speak to a doctor.