"Tgirl" stands for "transgender girl," which refers to the gender identity of the person involved in the scene. In this context, it is used as a tag for viewers who are interested in transgender content.
"Jerking" is another word for masturbation or self-pleasuring. This term indicates that the video features individuals engaging in this activity, likely involving hands and body movements for sexual stimulation.
Lastly, "HD" stands for High Definition, which means the video is of a higher quality with sharper images and better audio compared to standard definition videos. So, the overall meaning of this tag is: a high-quality pornographic video featuring transgender girls engaging in self-pleasuring or masturbation.