(1) A cellphone that works with only one cellular carrier. In the U.S., cellphones and smartphones purchased from the carrier are generally locked to prevent subscribers from easily switching to another carrier. However, there is a procedure to unlock the device for traveling to other countries or switching to another carrier. See
SIM lock,
jailbreaking and
Android rooting.
(2) The state of a smartphone that has automatically switched to its initial startup screen after a set period of inactivity. See
lock screen.