It just means word. Like a word, im assuming. Theres no other reason why it should mean anything else.
In Rap - it means "ain't that's the truth" "Agree with you" etc. Slang version is equivalent to the old fashioned "you said it" (agreement).
In text messaging, "NK" typically stands for "no kidding."
It may be a typo and the implied word may be good or google.
No comment!
Cf
LAO
"Uff" is a term commonly used in text messaging to express frustration, annoyance, or exasperation.
will call back
Tons of Yorkies.
Oh boy
It means hate
good to see you
"I love you"