Available with Standard or Advanced license.
Parcels can be unjoined from or rejoined to the parcel fabric layer at any time. When a parcel is unjoined it is removed from the parcel fabric layer and is listed in the Parcel Explorer window under Unjoined Parcels. An unjoined parcel can be opened, edited, and joined back to the parcel fabric.
You would unjoin a parcel if you wanted to change the geometry of the parcel and join it back to the parcel fabric layer. Parcel geometry can only be changed when the parcel is unjoined. To unjoin a parcel, right-click the parcel using the Select Parcel Features tool 
and click Unjoin. To join an unjoined parcel back to the parcel fabric layer, right-click the unjoined parcel in the Parcel Explorer window and click Join.
Parcel rejoining
Instead of unjoining and then rejoining a parcel, you can right-click a parcel in the parcel fabric layer and click Rejoin. The Rejoin command opens the Join Parceldialog box and displays the current join links for the parcel. You would use the Rejoin to view, edit, and change join links of a currently joined parcel.