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1.
a plant smoked as an alternative for marijuana
"Got some weed?"
"Nah, but for that some of that nganga."
by Koo J December 21, 2005
 
2.
Nga Nga reapeated provides the sound of an intense, nasty blowjob. This sound is made when the head of the penis reaches the back of your partners throat and engages the "gag" reflex. This sound is made better while the receiving partner humms a tune while doing the business.

Also, emulating this sound in an office setting toward an employee that is a dick sucker provides great humor.
I was giving it to that bitch good the ole Nga Nga! her mascara was running as well.

Do you see that brown noser always sucking up to the boss Nga Nga!
by Huskernsav May 25, 2011
 
3.
in tagalog, a conditional that it's opened widely
man : excuse me lady your dress very very nganga
lady : ohhhh so, are you see my underwear??
man : nooooo, but i see a crack of your cunt!!!
by alfredo stefano February 15, 2007