A hangover that is not evident upon waking up in the morning, but dominates your life two hours later.
At sunrise Joel bounced out of bed, gathered a crew up for brunch, sat down at the table, and proceeded to have his day destroyed by a ninja hangover that he had been harboring all along.
While trying to open a beer bottle at a party, you notice there are no bottle openers. So you use something at the host's house to open the bottle while breaking something in the process.
Phil: Hey Brit how did you open that bottle?
Brit: I just ninja opened it (ninja opening) on Christina's fence, i totally chipped a piece of the fence off.
A ninja nug is bud of weed stashed away somewhere that you miraculously find when you cant buy any more weed.
"dude we're outta weed"
"nah fool, i just found a 'ninja nug', its chill"
A Fap Ninja is someone who can masturbate on several occasions without ever getting caught.
Person One: "Whoa bro, I didn't even get caught, again!"
Person Two: "Whoa man, you're a real Fap Ninja!"
Someone who sneaks into a residence in which the dweller lives by themself, then deficates in their toilet leaving no visable toilet paper and then does not flush.
Jessie got home to her apartment after a long day at work. She stepped into the bathroom to take a shower when she spotted the foreign monster in the toilet bowl... she knew then the brown ninja had struck again.
Cricket team in which the ninja like skills of the team members have led to victory in the toughest competition of all. Ably led by tank, this side is predicted to dominate warehouse cricket for years.
The Cricket Ninjas are the best sporting team in history.
Ninja monday is a word used to describe things that are out of place, awkward, ludicrous, strange, or just don't belong.
Dali- "Did you see that ridonkulous picture of June on facebook?"
Kira- "Yeah. I tagged her as ninja monday. WHAT A NOOB."