The literal meaning is "to be put in jail." But we also use it for less serious confinement. Na-lock sa banyo? *Nakulong* ka. Stuck in a meeting that never ends? *Nakulong* ka sa conference room. Pinagbawalan kang lumabas ng magulang mo? *Nakulong* ka sa bahay. It's the state of being trapped, whether by bars, a door, or your boss's endless presentation.