Trunkin is when you send someone a drunk text. One you don't remember even texting because you are so intoxicated. The serial trunker checks their phone the next day in a panic, not knowing who or what they have text. When someone admits they have a serious trunkin problem, they will delete the text after they have sent it so when they wake up in the morning they don't know it even existed.
The girl had such a trunkin problem, she had to go to rehab. "Hi, I'm Jane and I have a trunkin problem."
Damn dawg, my ex keeps trunkin me in the middle of da night.