"3D Toon Tube" is a porn video tag that refers to animated adult content created using three-dimensional (3D) computer graphics, often featuring cartoon-like characters. The term "toon" is derived from the word "cartoon," and "tube" is an informal reference to a video. Thus, this tag represents 3D animated pornographic videos with stylistic elements similar to traditional cartoons. These videos are designed for adult audiences who enjoy both animation and adult content.