Learn Spanish (Latin America): No nos veremos hoy, salvo que coincidamos en el billar. - We will not see each other today, unless we coincide at the pool hall.

It follows the phrase salvo que (unless), which introduces a condition of exception. Phrases like salvo que, a menos que, and a no ser que always trigger the subjunctive because they set up a hypothetical situation that must occur for the main action to change.

Could I use a menos que or a no ser que instead of salvo que in this sentence?

Yes, absolutely. All three phrases mean "unless" or "except if" and can be used interchangeably here. A menos que is generally the most common in spoken Latin American Spanish, but salvo que is perfectly natural. All three require the subjunctive verb coincidamos.

Why do we need the pronoun nos in no nos veremos?

The pronoun nos is acting as a reciprocal pronoun here. Without it, no veremos hoy would just mean "we will not see today" (as in, seeing an object or a movie). Adding nos makes the action reflect back and forth between the subjects, meaning "we will not see each other."

Does el billar mean the game of pool or the physical pool hall?