When someone is zoned, their mind has gone somewhere else. Their eyes are open, they may even be looking straight at you, but nothing is coming in. It happens when a person is very tired, very bored, or under the effect of drugs or strong medicine. You are not asleep and you are not sick — you are simply not there.

This is informal, spoken English. Speakers usually say the full phrase 'zoned out' rather than 'zoned' alone: 'Sorry, I zoned out — can you say that again?' As an adjective before a noun you might see 'a zoned-out look'. 'Zone out' also works as a verb: 'I zone out in that class every week.' Note that this sense of 'zoned' has nothing to do with zones on a map, even though it is the same spelling as the town-planning word.

There is a friendly, harmless version of this. Everyone zones out sometimes — in a long meeting, on a bus, in the last ten minutes of a boring lesson. Saying 'I zoned out' is an easy, non-embarrassing way to admit you missed something. But be careful, because the same word can hint at drugs. If someone says 'he was completely zoned', the listener may well picture drugs rather than tiredness. The situation decides.

And here is a strange twist worth knowing. There is a nearly opposite expression: 'in the zone', which means totally focused and doing something brilliantly. 'Zoned out' is empty; 'in the zone' is full. Same little word, two opposite states of mind.