GTS stands for "Growth" or "Growth Transformation Sequence." In the context of adult content, it refers to videos that depict characters undergoing various forms of physical transformation or growth. This can include things like extreme muscle gains, sudden height increases, changes in body size or shape, or even transformations into other creatures or beings. It is often used as a tag for fetishes involving body expansion or growth, where the character(s) may expand to an enormous size, taking on a giantess or giant-like appearance. These videos can include elements of domination, humiliation, or simply fascination with the transformation process itself. GTS content typically features exaggerated visual effects and over-the-top transformations for maximum impact.