What constitutes job abandonment in Mississippi?

Not showing up would be good start

Whatever the employer decides it is. There is no legal definition of job abandonment in any state.

Most employers I have dealt with consider three days of not showing up for work or calling in to be job abandonment. Some allow two days. Some, like us, will can you the first day you don't show up and don't call unless you are able to show good cause for the absence AND convince us neither you nor anyone you know could inform us that you would be absent.