This is the 17246th most frequent Polish word.
zajęte
"Zajęte" means "occupied" or "taken."
The word 'zajęte' is used to describe that something (a seat, place, or room) is occupied or reserved and thus unavailable for use.
To miejsce jest zajęte.
This seat is taken.
Here, 'zajęte' indicates that the telephone lines are currently in use and thus unavailable for making calls.
Wszystkie linie telefoniczne są zajęte.
All telephone lines are busy.
In this context, 'zajęta' (feminine form) describes a person being occupied with tasks or activities, implying unavailability for other activities.