In the good old days, coconut milk could have meant only one thing, and that is the milky extract got out of freshly scraped or shredded coconut.
Fast forward to this day and age and there are several easier options available, which are not a patch on the real thing, but unfortunately it is not always possible to get down to making your own when one is constrained for time and when the coconut available itself isn't that great.
So in order of preference, my choices are:
1. Fresh coconut milk, extracted out of a freshly shredded coconut
2. Coconut milk extracted out of frozen shredded coconut
3. Canned coconut milk or powdered coconut cream dissolved in water - depending on the usage, I prefer one over the other.