As an initialism bak
is basic aeronautical knowledge , an initial theory course for trainee pilots.
As a noun pak is
packet, pack or pak can be riff-raff, plebs, the underclasses.
bak
English
Abbreviation
(Abbreviation)
(head)
(text messaging) back (any sense)
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pak
English
Derived terms
*
*
* Tetra Pak
* Z-pak