last to know (ltk)

Phrase: When you or someone else finds some sort of information, usually a cultural or pop culture reference/event, and proceeds to share it with everyone else. Except that pretty much everyone one else in the world already knows. This can be any form of news, media, observation, or anything on the internet. Usually found on social networking websites.

Expressed in short form as "LTK". Can be used in text messages or chat.