Meaning : (of facilities such as telephones or lavatories) unavailable for use by anyone else or indicating unavailability. (`engaged' is a British term for a busy telephone line).
Example :
Her line is busy.
Receptionists' telephones are always engaged.
The lavatory is in use.
Kept getting a busy signal.
Meaning : Currently being used.
Example :
Robots are in use throughout industry.
In use meaning in Bengali (Bangla).