Stack:

Stack is a callout for concentrating players or utility in one area, most often by grouping teammates on a single site, choke, or objective.

In VALORANT, stacking is used to strengthen a defense, commit to a fast retake, or overwhelm one part of the map with numbers. It can also describe piling multiple abilities onto the same spot or target, such as layered smokes, flashes, or damage.

Related: Rotate, Retake, Execute