Dispersal field
From Memory Alpha, the free Star Trek reference.
A dispersal field is a type of energy field used by the Borg, which interferes with sensor and transporter function.
In 2375, the Borg Queen activated a dispersal field around the central chamber of the Unicomplex, to prevent the Delta Flyer from beaming out Kathryn Janeway and Seven of Nine. Janeway disabled the field by firing at the power node above the Queen's alcove. (VOY: "Dark Frontier")
In 2376, a Borg cube crewed by only five neonatal drones approached the Delta Flyer undetected using a dispersal field. (VOY: "Collective")
