A smash in tennis is a shot that is hit above the hitter's head with a serve-like motion.
[1][2][3] A smash can usually be hit with a high amount of force and is often a shot that ends the point.
In his 1979 autobiography Jack Kramer, who had a fine overhead himself, devotes a page to the best tennis strokes he had ever seen.
The swing is an upward throwing motion, making the execution of the shot almost identical to a serve.
The positioning and footwork are more similar to a volley which is usually hit with a strong forward weight transfer from inside the court.