Tongue Tied

A holowhip is a device that generates an energy whip, similar to a light saber from Star Wars, but the energy is

"I'm going to lash you to within an inch of your life..."

more "flexible". It can allow a human to bestow physical violence to a hologram, something Dave Lister threatened to do to Commander Binks, if he didn't leave Starbug in the Series V episode Holoship. It can also be held by holograms as well (possibly because there is a hologramatic component to it) to harm humans with, as the Low Rimmer did to Lister in Demons & Angels.

The reason for this device is most likely to allow holograms to subdue humans, despite holograms having (almost) no physical form or humans to subdue holograms which have gone insane or have contracted a holovirus. It doesn't appear to have lethal capabilities as, in it's only demonstration, it only causes pain strong enough to incapacitate its target, though the Low Rimmer did mention his intention to "lash you within an inch of your life", hinting it might have the capabilities to go beyond even that threshold.