MIAMI (CBSMiami) — You may think you’re good at monitoring your teen’s texting activities, but there are new apps and texting lingo designed to keep parents in the dark.

It’s not unusual to see teens texting away on their cell phones.

But, as a parent, do you really know what they are saying?

Carol Coleman, the mother of a teenage girl, was surprised to learn that the letters ‘l-m-i-r-l’ means ‘let’s meet in real life’.

But another mother, Michelle Burgess, successfully guessed what ‘g-y-p-o’ means.

“Get your pants off,” Burgess said.

An online service, called Smartparents, allows parents to see what their children are saying on their high-tech devices.

“There’s been kind of an arms race between parents and technology and parents are losing,” says Gerry Polucci, president of Smartparents in Brookline, Massachusetts.

But even if you think you’re monitoring the plans you pay for, there are apps that allow teens to call and text for free without a data plan.

“It’s scary in a way, just not knowing,” said Coleman.

Other apps text photos which allow those pictures to disappear from the receiver’s phone in seconds.

According to the Journal Of The American Medical Association: Pediatrics, 28% of teens report they’ve texted naked photos of themselves.

And many of those teens don’t realize that the picture isn’t always gone for good.

“The receiving person can take a screen shot of that on their iPhone,” says Polucci.

Besides risqué photos, some chat terms are anything but innocent.

The letters ‘g-n-r-n’ means ‘get naked right now’ and ‘i-m-e-z-r-u’ means “I’m easy are you’.

Teens use these abbreviations and hundreds more to ‘k-p-c’ which means ‘keep parents clueless’.

But they’re not alone.

Tim Woda says an online sexual predator used teen chat abbreviations like ‘a-l’ meaning ‘age and location’ to target his 14-year-old son.

An arrest was made and the suspect pleaded guilty to sexual solicitation of a minor.

‘This particular predator had over 250,000 lines of sentences in code written in his computer where he was targeting and grooming children,” said Woda.

Experts advise parents to monitor the apps that their children are using and stay on top of the texting lingo.