(adjective)
separated or detached, not connected, or removed from reality, used figuratively to describe a person;
e.g. The lamp is disconnected, which is why it isn't working. He seemed rather disconnected and clueless.
(adjective)
disjointed, not connected by a logical sequence and thus not forming a reasonable whole;
e.g. The parts of his argument felt disconnected so I wasn't sure what exactly he wanted.
(verb)
detached something, disrupted or broke the connection between things or people, for example cut off the power supply of an electric/electronic device;
e.g. She disconnected her headphones from the device. He disconnected the computer from the wall.
(verb)
disrupted or ended the connection that sustains a phone conversation;
e.g. She disconnected the phone call when we had finished speaking.