v. t. 1. To make inactive; to render ineffective; as, to deactivate a bomb; to deactivate a machine; to deactivate the alarm. The deactivation of a machine or device is usually a reversible process; switching off an electrical device may be referred to as deactivation. To render an enzyme or catalyst ineffective is more commonly referred to as to inactivate. [ PJC ] 2. To disband (a military unit, or other group); to discontinue (a group activity); as, to deactivate the regiment; to deactivate the investigation. [ PJC ] | 