What is the meaning of Rehab?

Rehabilitation, especially to treat the use of recreational drugs.

An institution for rehabilitation.

A brief period of time spent away from the fire by a firefighter at a fire scene, for purposes of recuperation.

To rehabilitate.

a rehab; an institution for rehabilitation

to rehabilitate; to return (someone) to good health after illness, addiction, etc.

rehab ((institution for) rehabilitation)

Source: wiktionary.org