....
However this is a rather Eath specific definition.
It was for a long time thought that chirality was a symmetry of physics, that the laws of physics were the same for left handed as right handed.
However in 1957 it was demonstrated that some radioactive decays under a magnetic field occur with a predominant handedness.
http://universe-review.ca/I15-31-parity.jpg
In this picture a cobalt atom in a magnetic field emits fewer beta rays in the direction of the field than against it with a certain spin
This gives you a definition of left and right handed spin good for the entire Universe
It may be a bit obtuse but as I say it was only discovered 50 years ago ( and the discoverers got Nobel prizes ) It was damn hard to find - and important because it shows that deep down the Universe does care whether or not you are right or left handed