What is the exact meaning of "manoeuvring" when said by ATC in reference to traffic? In the UK, when receiving a basic service, sometimes the ATC unit passes traffic information. They may say it like this:

“Traffic to your three o'clock, similar level, C172 manoeuvring.”

What exactly is the word “manoeuvring” conveying? Is there a defined point where an aircraft is manoeuvring and when it is not?
To add to @HiddenWindshield's answer, it's explained in UK's CAA Radiotelephony Manual CAP 413:

Traffic Information and Avoiding Action Phraseology
5.21 Relative movement should be described by using one of the following terms as applicable:
(...)
5. 'manoeuvring' where the conflicting traffic’s flight path and/or level information is unpredictable and/or showing significant variation.