1. (verb) to protrude (especially of the tongue), poke out the tongue. (From the MÄori Dictionary Online)
They are two different performance components. Pukana is the dilating of the eyes and whetero is the protrusion of the tongue performed by a male only.
The National Rugby Team, All Blacks, always do a Maori War Dance called 'Haka', before their game. In this, a stage of the dance is called, 'Whetero', the protruding of the tongue, (pushing out the tongue.)