Loss of a Leaving Group Definition:

One of the four arrow-pushing patterns for ionic reactions.

Loss of a Leaving Group Explained:

A leaving group, LG, is an atom (or a group of atoms) that is displaced as stable species taking with it the bonding electrons. Typically the leaving group is an anion (e.g. Cl-) or a neutral molecule (e.g. H2O). The better the leaving group, the more likely it is to depart.