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1.
Acronym for "Welcome To The Internet"
Used when someone is new to the internet, or just joined an online conversation.
*Brit has joined the conversation*
Ricky says: Welcome to the internet
Bill says: WTTI
by Xanderrrrrr April 21, 2009
 
2.
Short for "Welcome to the Internet." Used sarcastically when someone shares an outdated video or meme and thinks it's the funniest thing ever.
"OMG have you guys seen Missing Missy? LOLOLOL." "WTTI bro."
by Denim_Chicken December 30, 2011