Usually set-up in non-verb form, sometimes setup in noun form particularly.
1. (Of a player or referee) to place the balls (and other items, if applicable, such as skittles) properly for the beginning of a game: "In eight-ball, properly setting up requires that the rear corners of the rack not have two stripes or two solids but one of each." For most pocketbilliards games this is in a racked pattern, but the term is applicable more broadly than "rack", e.g. in carombilliards and in pocket games like bottle pool. Contrast layout.
2. (Of the game equipment) arranged properly for the beginning of a game: "set up and waiting for the break", "an improper set-up"
3. (Of a player, passively and specifically) to have good shape – to be in a favorable position for making a shot or other desired play ("is set-up on the 9", "could be set-up for the corner-pocket after this shot")
4. (Of a player, passively, generally, and chiefly US) to be in a favorable position for, and with a layout conductive to, a long run (UK: break) or complete run-out: "a crucial miss that left his opponent really set-up"; compare (chiefly British) "in the balls"
5. (Of a player, actively) to use position play to move one or more specific balls to specific locations with a specific goal in mind, usually pocketing (potting) a specific ball or getting an easy out, but possibly a safety, nurse or trap shot; in short, to get shape: "She set up on the 9-ball with a careful drawshot." The meaning can be inverted to indicate poor play on the part of the other player: "Oops, I just set you up for an easy win when I missed like that."
6. (Of a table layout) comparatively easy to completely run out, e.g. because of a lack of clusters or blocking balls: "looks like a nice set-up for a quick out", "this table's totally set up for you"
7. (Of cue ballposition more specifically): having good shape – comparatively easy to use to some advantage, such as continuing a run (UK: break) or playing safe: "The cue ball's set up for an easy side pocketshot."
8. (Of a shot or strategy) the result of position play (careful or reckless): "Playing the 6 off the 8 was a great set-up to win", "That follow shot was a terrible set-up for the 6-ball."
9. (Of a hustler) to successfully convince a fish that one is not a very skilled player and that gambling on a game will be a good idea: "That guy totally set me up and took me for $200." Such a hustle is a setup or set-up.