You're using Chrome, so look for it in Chrome's Task Manager:
https://support.google.com/chrome/answer/95672?hl=en
If it's listed there, then control it from there. That task mgr should also identify what kind of process it is.
If it's not listed in Chrome's Task Manager, then use Activity Monitor to discover the process's Parent Process ID (PPID).
It should be listed for the process when you get info on it. Try selecting the process and clicking the circled-i icon in Activity Monitor's toolbar. If its PPID is Chrome, then it's a Chrome process that Chrome is somehow failing to manage. If its PPID isn't Chrome, you can sort the processes in the list by PID (Process ID) and learn who its parent is.
Here's more info on using Activity Monitor:
https://support.apple.com/en-us/HT201464