What is hair-pinning on Cisco ASA firewall

Hair-pinning also called as ‘U-turn ‘.The ASA includes a feature that lets a VPN client send IPSec-protected traffic to another VPN user by allowing such traffic in and out of the same interface using the command ‘same-security-traffic permit intra-interface’

In another application, this feature can redirect incoming VPN traffic back out through the same interface as unencrypted traffic. This would be useful, for example, to a VPN client that does not have split tunneling but needs to both access a VPN and browse the Web.