Your tongue can actually tell a lot about your health, search tongue diagnosis TCM
Traditional Chinese Medicine,
I suggest you visit a Chinese acupuncturist, and have them look at it, they can tell you the exact cause, and what its indicating.
Check this link below for more information.
http://www.sacredlotus.com/diagnosis/tongue/index.cfm
Look on another website
The line of your tongue is there because when the body is forming it is split into sections. The line shows where the face sections came together.
what is center line plan construction
It means to kiss
If you stick your tongue out, you poke it out of your mouth.
It's slang for going down on a girl aka tongue action.
No passing.
divided highway
It means that your lane cannot pass.
no passing on your side of the road. only the other side
No passing by traffic travelling in your same direction.
No passing when driving in that direction while it is solid.
No passing, when it is on the other side you can pass.