Definition
To begin a festive celebration and rejoice for someone's long-awaited return.
Origins
From the parable of the prodigal son in the New Testament.
How People Actually Use It
To host a major celebration. (Reference to the Parable of the Prodigal Son; mentioned in the Elton John song, "Bennie and the Jets.")
"Dave finally graduated; he's going to kill the fatted calf tomorrow evening...should be a blast!"
Source: Urban Dictionary