Transwarp beaming is an advanced transporter technique that can send a person across great distances or onto a vessel travelling at warp speed.
In the alternate reality created by the Narada's incursion, the older Spock gave Montgomery Scott an equation that Scott himself would develop in the future. Using it, the two beamed from an outpost on Delta Vega directly onto the Enterprise while the ship was at warp, and Scott materialized inside the ship's water pipes.
The technique appeared again when John Harrison used a portable transwarp transporter to escape from Earth to the Klingon homeworld Qo'noS.