The phrase you state at the end of an argument or statement to create an illusion of credibility when in reality you don't actually know if what you stated is true but still have personal trust in your knowledge. By stating "look it up" you are actually hoping the person won't look it up and just believe you on the spot.
"Vaccinations are evil. Look it up"
"Humans all deserve to die, we are filthy viruses, look it up"
"I am always right, look it up"
by 1sagain June 14, 2017
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The thing you say when you know you're wrong but just wanna waste someone's time.
Me: I'm telling you, Patrick Duffy played Spiderman.
You: Umm. No. He did not.
Me: Look it up.
You: Sigh..
by Bonch Nifkin July 21, 2011
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A completely bitchy thing to say when asked a simple question. A great way to set a horrible example for children by acting immature and adding fuel to the fire.
TV Interviewer: Madonna, what do you think about Lady GaGa's song 'Born This Way' reportedly sounding a tiny bit like 'Express Yourself'?

Madonna: She seems reductive.

TV Interviewer: What's reductive?

Madonna: Look it up. *sips tea*
by cmoneyrules February 17, 2012
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An answer to every question to children under 20.
Child: Whats porn?
Mother: Look it up.
by njgshqehgo[gho October 10, 2018
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A definition that you look up every underlined word it possesses.
See Look it up
by Mallory The Great July 30, 2008
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1. What you say to someone who hasn't done the reading, doesn't have any idea what she is talking about, and is simply insisting on her opinion; because opinions, and doesn't know what that means either.

2. In social media, how someone who knows the subject dismisses someone who doesn't. (See Bye, Felicia).
Q: What do you mean, the United States isn't the sole reserve currency issuer in the world?
A: UTFI - IMF SDR - and get back to me.
Q: What does UTFI mean?
A: Look It Up
by UTFI April 6, 2019
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