Verb:
1) To think extremely irrationally as a result of being horny.
Dick thinking frequently leads to moronic behavior. This is primarily present in men, although a minority of women will experience this. A myriad of stupid behavior men engage in can be explained by this phenomenon.
John(horny): Well, my ex-girlfriend Lisa called. She asked if I would drive 300 miles to feed her cat over my vacation. I think its a good idea, maybe she'll put out.
Rob: What are you fucking nuts? You're dick thinking man! This broad's got a boyfriend and has been rejecting you for years.
John: Okay I won't feed the cat. Thanks for stopping me, I was dick thinking for sure.
A pun on "wishful thinking," it's when a man lets his own sexual interest in someone strongly color his judgement regarding the person's reciprocal interest in him. It makes him interpret every gesture from his object of interest as a come on, even when it clearly isn't. This is known as clitful thinking if it's a woman.
Him: "So the new hot intern says 'good morning' to me when she comes in to work, and once commented on my desk picture of my kids - said they were cute. She's totally into me. I'm gonna try and hook up with her at the office party."
Friend: "I get that it's been tough for your after the divorce, but that's just dickful thinking. She's not into you, now stop before you get an HR complaint."
OR
Him: "Pete high-fived me at the trivia night - I'll bet he's secretly gay and would let me blow him."
Friend: "You have no gaydar and a bad case of dickful thinking. The boy's straight."
To suck dick so well that person makes a person come the hardest they ever had!!
After Jason went to the underground sex party he had a hot chick Think Dick to him for the first time.