NTOSDEF.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the NTOSDEF.H header at

d:\th\minkernel\ntos\inc

and draws from it the following type definitions:

Line Number Type NTOSP.H
80 struct _PP_LOOKASIDE_LIST 515
97 enum _KTHREAD_TAG 532
125 struct _KERNEL_STACK_SEGMENT  
144 struct _SYNCH_COUNTERS  
243 struct _FILESYSTEM_DISK_COUNTERS  
280 struct _KENTROPY_TIMING_STATE  
301 struct _KDPC_LIST  
310 struct _KDPC_DATA  
331 struct _KSHARED_READY_QUEUE  
351 struct _IOP_IRP_STACK_PROFILER  

The header NTOSDEF.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).