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1.
NKA
It is SOP for soldiers in combat situations to have their blood type readily visible on their uniform, so that if blood transfusion is required, time is not wasted deteriming blood type. Some units also require any allergies to be visible, and if the Soldier has No Known Alergy (NKA) this info is stated. This is commonly seen on Rangers, Special Forces, Navy SEALS and other elite forces.
A soldier that has ''NKA'' sewn on his uniform has no known alergy.
by Bear67 July 22, 2006
 
2.
1. A word which can be used in the expression of shock and embarrassment after a mortifying experience such as getting thadded or being mistaken for a hooker.

2. This applies only to the queens of bull dykes, people with the plumber's ass, and the netherworld.
Lisa: "Hey, what's up?"
Nicka: "Um, last night I got laid ..."
Lisa: "Oh?"
Nicka: "By my own father. I WAS DRUNK OKAY?!"
Lisa: "OH NO YOU DIDNT!!"
Nicka: "I did. N-KA!"

by AJ R. Craig April 14, 2009
 
3.
"Never Known As" A term used by someone who is trying to be witty and see if you are listening.
Hi my name is Phil, n.k.a. Johnnie Wad.
by Torrez74 August 21, 2008