From the anime Jojo's Bizarre Adventure, it is to run away while thinking of a better plan. Sometimes referred to as a tactical retreat
Smokey: Do you have any backup plans to kill this thing Jojo?
Joseph Joestar: You bet I do!
Smokey: Huh? Really?
Joseph Joestar: Yeah, I've only got one left.
Smokey: What is it?
Joseph Joestar: It's time to use my legs
Smokey: How so?
Joseph: NIGERUNDAYO, SMOKEY
What you yell while running away from an angry black mob after saying the nword(either intentionally or unintentionally)
Me: Heynigga Black guy: WTF did you say cracka? Hey homies beat this white guy up, he said that word.
Me: I'll deal with you using my legs.
Black guy: show us what you got.
Me(runs away): Nigerundayo.
the act of saying the n-word in front of a black guy and then running away, particularly if you are in a popular japanese animated television series titled "JoJo's Bizarre Adventure", which aired in 2012, originally written as a manga by the popular mangaka "Hirohiko Araki" (1960-present)