To submit something; to give
He turned in his paperwork to the main office.
To relinquish; give up; to tell on someone to the authorities (especially to turn someone in)
My nosy next-door neighbor turned me in for building my garage without a permit.
To go to bed; retire to bed
I'm tired, so I think I'll turn in early tonight.
To convert a goal using a turning motion of the body.
To reverse the ends of threads and insert them back into the piece being woven so they do not protrude and eventually unravel.