A symbol used when someone uses a 4 instead of a 3 when making a heart symbol <3. This can be done on accident making the user look stupid or it can be done on porpose meaning the user more than <3's them.
Tiffany - "Okay. See you then - <4"
Mike - "You're an idiot."
Jen - "I love you more than anything in the world. <4"
Originally coined in 2004 by one Michael John Keegan, <4 was created to be a play on the ever-popular internet code for love, <3. It has since become a fad, thought by many to have originated as a typo rather than an entity all its own, and has been reabsorbed into the tween culture that prompted its creation.
Phrases utilizing <4 require unusually hammy dialogue; e.g., OMG I <4 U.