A hard-light hologram was a hologram which was solid.
The holo-cubes used by the Plume Coteries allowed the consciousnesses housed within them to project hard-light avatars of arbitrary sizes and shapes. (PROSE: The Cactus and the Corpse [+]Aristide Twain, Horrors of Arcbeatle (Auteur, Coloth, Arcbeatle Press, 2023).)
Phayke was a planet inhabited by hard-light holograms. (COMIC: Spam Filtered)
Hard-light holograms were used on the Orient Express to deceive passengers into believing the train was normal, creating hologram furniture and people. (TV: Mummy on the Orient Express)
Strax's fighting drone was an example of a hard-light hologram. In 1894, Strax tinkered with the drone causing it to malfunction and begin roaming Paternoster Row. Most of the residents thought that they were being hunted by a Ghost and blamed Madame Vastra for it. (PROSE: The Spectre of Paternoster Row)
The Fifteenth Doctor told Kid that holograms were usually useless you were the Doctor who could convert them into hard-light holograms which could hurt. The Doctor converted a hologram of himself created by Gary Gabbastone on Harmony Arena into a hard-light hologram which he was able to use to electrocute Kid as a form of torture. The Doctor later had Gary fashion the hard-light into a tractor beam to rescue the 100,000 people trapped in Harmony Arena's mavity shell. (TV: The Interstellar Song Contest [+]Juno Dawson, Doctor Who series 15 (BBC One and Disney+, 2025).)