Trapped Gas
When you have gas that is inside your body but doesnt want to come out. Some what like being constipated but instead of stool its gas.
"I ate those boiled eggs earlier today and now i have trapped gas."
Gas Trap
When you fart in a car and roll up and lock the windows so your companion is forced to smell it.
He had to be rushed to the hospital after suffering complications from a Gas Trap. Paramedics say the perpetrator ate Taco Bell.