teen girls selfies Say cheese for the finstagram. Shutterstock

On a recent train ride, my friends overheard two teenage girls talking about a trend at their school called "finstagram." No, not Instagram. Finstagram. 

When they told me about the bizarre conversation, I was intrigued. A quick Google search for "finstagram" led me to Urban Dictionary, where a definition for the term was uploaded in 2013. 

Apparently, a finstagram, or "finsta" as the youths say, is a secondary Instagram account, where teenagers post funny pictures, sans Valencia filters and VSCO cam edits. It's meant to be a more "real" version of Instagram, only to be shared with close, trusted friends. 

Here's the full Urban Dictionary definition:

finstagram urban dictionary Urban Dictionary

"Normal Instagram pictures are usually edited to make the people in them look really good, like whitening teeth and getting rid of acne," New Jersey high-schooler Arman Julia told Tech Insider of the trend. "Finsta pictures aren't filtered and are almost always bad pictures of the account owner. They're just something fun, they're meant to make people laugh."

Here's a silly example from Arman Julia's finsta, which she co-runs with another friend from school. 

"On your finstagram, you post the grossest photos and videos," Sara, a 15-year-old from New York, told TI. "And then you and your friends laugh about how funny and gross they are."

Sara's regular Instagram, or "rinsta," has over 200 followers. By comparison, only 25 people are privy to her finsta, which includes embarrassing photos, like a recent "triple chin" selfie. Sara declined to share that selfie with TI. 

The finsta trend has been growing for some time now. To create two Instagram accounts, you need two distinct email addresses. In February, 17-year-old Eric Herber wrote a post on Medium where he weighed in on the trend that he said seemed to be taking over his high school. 

"Finsta is sort of a combination between the content you would post on Snapchat inside the instagram app," Herber explained in his post. "It is not just normal to have a finsta, it is expected." 

Elle Magazine also weighed in on finstagrams this summer, labeling them a place where some teenagers, mostly girls, hide their real lives from the prying eyes of parents and teachers. 

Still, the teens Tech Insider spoke with don't seem to be taking themselves, or their finstas, too seriously.

"It's a fun way to post pictures that could make another person's day," Yooree, a 17-year-old student in Florida, told Tech Insider. 

Like Arman Julia and Sara, Yooree also said she posts pictures to her finstagram to "make people laugh." Still, she says she wouldn't want her finsta falling into the wrong hands. 

"My finstagram has 30 followers versus my regular account, which has over 600," Yooree said. "It is private, mostly since the pictures would be embarrassing if seen by certain people."

We've reached out to Instagram to get their take and will update if we hear back.

Despite their growing popularity, it doesn't look like finstas have become totally ubiquitous in the teen world. At least, not yet. 

"I've actually never heard of them," Gabby, a Massachusetts high school senior, told Tech Insider when we asked her about finstagrams. "Can I assume it's about mermaid tails?"