Meaning to beat someone to the punch. This is especially true in the comments thread of a Full Metal Alchemist post, and most specifically in response to a Nina Tucker meme.

A portmanteau of carpe diem, a Latin phrase that means “Seize the Day!” and DM, which stands for Direct Messages. This word means seizing the day via DMs.

The phrase originally started in the Facebook group Tavern At The End Of The Internet following the propensity for a staff member always commenting ‘These jokes never get old, just like Nina!’ on Nina Tucker memes (from Fullmetal Alchemist). The use has expanded to being said when getting in right before the closing off point of something - getting in just before the red light, being the very last one to score a ticket for something, etc. It’s rapidly growing in popularity across groups and even into irl situations, bamboozling friends and coworkers.

Original gag:
Step 1: See a Nina Tucker meme

Step 2: Look to see if Tim Brockway has commented ‘These jokes never get old, just like Nina!’ yet

Step 3: If he hasn’t, then comment ‘In Before The Brockway’. You’ve won this round! If he has, then he wins.

Step 4: Rinse and Repeat!

When someone posts on a meme before the person that's always first to post.