acronym for "I know, right?" - the rhetorical response to any statement of undeniable truth. Used in IM or text based conversations (also, "IK,R?") and NEVER acceptable as spoken aloud (eye kay are.)
Hammer666: Wow, that other definition sucks.
Lizard420: IKR? I'm making a better one.
邮件由 email@example.com 发出。我们决不会发送垃圾邮件。