To tinker with something is to change it or try to fix it. The resulting change is usually small. You can use "tinker" for machines, computers, plans, systems, organizations, or any variety of things that have small moving parts.
Mark enjoys tinkering with old cars.
Vanessa likes to tinker with computers.
Tinkering with your cell phone might invalidate the warranty.
Our supervisor is always tinkering with the work schedule.
Brian found an old, broken watch in an antique store. He tinkered with it a little and got it to work.
Bill tinkers around with small motors in his workshop.
If you tinker around with a broken object for a long enough time, you might be able to figure out the reason why it doesn’t work.
Scientists who tinker with Mother Nature are not always happy with the results they achieve.