Freely available; ready to be taken.
Example: 1) After Mr. Mortimer passed away, no one could find his will, so his estate is up for grabs.
2) I don't want my sandwich--it's up for grabs, if anyone wants it.
Etymology: When you 'grab' something, you reach for it very quickly. When something is up for grabs, it is out in the open, waiting to be grabbed by whoever wants it.
Fonte: Knights English