Bak praktak!

In full: Bak praktak sekut tarl les oc!

Pronunciation guide: 'Bak' as in English 'Buck;
                     praktak, both a's as the 'u' in English 'Buck', so 'prucktuck';
                     'sekut' as in French 'écoute' with an 's' in front,
                      so 's'écoute';
                     'tarl' as in the first part of 'tarlton'
                     'les' 's' is hard and not soft as in 'less';
                     'oc' as in 2nd part of 'knock', so 'ock'

This alien phrase is akin to 'whatever' but not as impolite. It is not meant to offend.
en.wikipedia.org/wiki/Whatever…

It is indicative of irritation, annoyance, frustration, with a conversation or situation, to the point of not caring anymore. In fact, aliens of Nurog use this phrase not native to their own tongue to emphasize that speech is now no longer desirable, or a state of indifference has been reached or is called for.