virsh send-process-signal domain-ID PID signame command sends the specified signal (identified by its signame) to a process running in a virtual domain (specified by the domain ID) and identified by its process ID (PID).
Either an integer signal constant number or a symbolic signal name can be sent this way. Thus, for example, both of the following commands send the kill signal to process ID 187 on the rhel6 domain:
virsh send-process-signal rhel6 187 kill
virsh send-process-signal rhel6 187 9
For the full list of available signals and their uses, see the virsh(1) and signal(7) manual pages.