To make something inactive or ineffective. The technician will deactivate the alarm system before starting the repairs.
To turn off or disable a device or function. You need to deactivate the airplane mode to receive calls.
To render a chemical or biological agent harmless or inactive. The lab team worked to deactivate the virus in the sample.
To make an explosive device safe by rendering it incapable of detonation; disarm. The bomb squad deactivated the landmine before the construction crew arrived.
To remove (a person, unit, or equipment) from active service or duty. The regiment was deactivated and its soldiers reassigned to other posts.