An expression signifying an EXACT undertanding/agreement of what the speaker is saying.
Spoken very loudly or with higher intonation. Hand motion is generally used with speech.
"Can you beleive she wore that?" "I KNOW!"
"You would think the professor would give us a study guide." "I KNOW!"
When you want to imply you totally get what the other person's sayin'... ususally spoken with an emphasised "know".
Girl 1 : So then he told me, "I'll call you" and didnt even kiss me goodnight! I mean, hello?!
Girl 2 : i KNOW! Men can be such boors at times!