no-execute bit
The flag in a page table entry that forbids running the bytes in that page as instructions, so data such as the stack can't be executed.
The no-execute permission (x86-64 NX/XD, bit 63 of the PTE; ARM64 UXN/PXN execute-never; RISC-V: X bit clear) makes an instruction fetch from the page fault; Windows calls its use DEP (Chapter 37).
See also