The Sealing Spell is a spell capable of sealing an entity in any kind of object.
Roughly 75 Million Before Age, during an argument between the God of Destruction Beerus and Old Kai in one of their coordination meetings held every 1,000 years, the short-tempered Beerus used a sealing ability in order to seal the Old Kai inside the Z Sword, due it not being proper to outright destroy the Sacred World of the Kais.
Roughly 5 Million Before Age, the Sealing Spell was used by Bibidi to take a break after Majin Buu absorbed the Grand Supreme Kai, trapping the Majin in a Sealed Ball. This incantation is unpronounceable for humans; putting it into letters, it would be something like "Nuwemwittsimwawaay". When he died, Bibidi left the spell behind in his notebook.
In Dragon Ball Z Gaiden: Shin Saiyajin Zetsumetsu Keikaku - Uchū-Hen, Goku finds a sealing tag on the first planet he goes to and can use it to seal Dr. Raichi.
While Babidi said he learned the incantation to seal away Majin Buu from the notebook of his father Bibidi, he never had the chance to use it in his lifetime. After reviving Majin Buu in Age 774, whenever Majin Buu disobeyed Babidi's orders, Babidi threatened Buu with the spell and thus Majin Buu then followed Babidi's orders, not wanting to be sealed up once again. Eventually, Majin Buu used the weakness of the spell against Babidi: by preventing Babidi from speaking via strangling, Majin Buu prevented him from uttering the incantation required to activate it.
In Dragon Ball: Xenoverse, Chronoa is shown to be quite skilled at using Sealing Spells as she sealed Demon God Demigra inside to Crack of Time and is even proficient enough to seal Démigra's self destructing Majin Emblem in a sphere of energy, allowing her to throw it away before it detonated, saving herself, Future Trunks, and the Future Warrior. This marks the first time a sealing technique is used to seal something other than a living being and being used to counter other forms of magic.