Term
Drop Serve
A serve where you drop the ball from your hand and hit it after it bounces.
A serve where you drop the ball and hit it after it bounces (Section 2, Definitions, 7.D). The swing rules for the volley serve (swinging from low to high, hitting below the waist, and so on) do not apply to it (7.C, 7.D.6, How to serve (volley serve and drop serve)). There is a rule that you must let the ball fall from a natural height, without pushing it out or throwing it down (7.D.1, 7.D.2).
How to read the sources: numbers like (8.F.4) are rulebook sections, and links are outside sources. An "Author's note" is the author's personal experience, not an official rule.