Mass debating is the way Chris pronounces "masturbating".
When he first started mass debating, he did so by lying face down on his bed (also known as prone masturbation) and rubbing his duck with a washcloth. In early 2009 he would sit on the bathroom washbasin during the act. In Ivy's Q&A it was mentioned that Chris has used his pillow, folded in half, as a masturbation tool.
—Chris, using mass debating.
While it is assumed by many that Chris has a voracious sex drive and spends every day whacking it, the truth is quite different. Rather, Chris has admitted to whacking off at least twice per week (based on chats, it seems that he limits it to twice). Possible factors for this include the fact that he has a bent duck which would most likely make masturbation painful, and he probably struggles to get/maintain an erection owing to his obesity and general poor health. The sex audio with Julie seems to indicate that it takes Chris around 20 minutes to orgasm, which means that masturbation for Chris must be physically exhausting. Chris also believes that he has a limited sperm count which may have him limit his sexual activity. Also, Chris was at one point prescribed the antidepressant paroxetine (Paxil), which (from what was heard from him) caused some sort of sexual side effect, perhaps slowing down his ability to orgasm.
In January 2018, Chris claimed that he no longer masturbates. This could be a result of estrogen treatment (decreased libido is a known side effect).
On November 18th 2018, Chris's Twitter uploaded a video of himself mass debating his flaccid duck while singing the song All-Star by Smash Mouth. The video is obviously coerced and posted by trolls and Chris was noticeably stressed and uncomfortable during the act.