Fusion forms (SSJJ)

Fusion forms are forms that are the result of fusion causing two or more distinct forms to be merged into one new one.

Hybrid Super Saiyan
Hybrid Super Saiyans are result of two different Super Saiyan forms being fused together by two different people or the same people. So there as been Future Super Saiyan-Super Saiyan Rosé, Potential Unleashed-Super Saiyan Blue, Super Saiyan-Legendary Super Saiyan, and Super Saiyan Blue-Legendary Super Saiyan 3 in Dragon Ball Advanced.

Other forms
Other forms of Fusion forms are Dicell Jr. being a fusion of any of his forms, and Cell Jr. in his Perfect Form-like appearance, Pooler's forms, and Naraku's fusion.