I was eleven-years-old and had just discovered the joys of jacking off. My parents were driving back in our station wagon one evening after a day on the Lake with their best friends sitting in the back seat while I was lying on a comforter behind the back seat. The adults had been talking and joking for the first thirty minutes then things had got quiet.
Mrs. P who was a forty something nurse that had a good figure and in retrospect was very sexy, was sitting up with her arm draped over the back of her seat while her husband was sleeping with his head on her lap. I was lying behind the back seat with my knees up and nearly asleep when Mrs P's hand brushed my leg. I didn't think much about it at first, but she continued to soothingly move her hand up and down on the top of my leg and it wasn't long before I had a raging hard on.
After several minutes her rubbing motion slowly moved lower and lower until she was lightly grazing my shorts that was only an inch or two from my cock. Then much to my surprise and delight her hand reached down and caressed my cock through my shorts. I honestly thought I was going to die. My heart was beating so fast and hard that I was afraid her husband and my parents could hear it. I lay there totally motionless while she lightly massaged my cock for what seemed like an eternity. She then reached up the leg of my shorts, moved my underwear aside and put her hand directly on me. The legs of the shorts were loose so it didn't take much effort to free my cock. After teasingly touching ever part of my balls, and cock she began ever so slowly to move my foreskin back and forth for a few seconds, followed by rubbing the very head of my cock, followed by more up and down motion. After maybe a minute of stimulation I began to feel those tremendous spasms and within seconds I had the largest climax that I have ever had. Because of my age the amount of cum might not have been as much as an adult, but it felt like I had shot cum everywhere. After I came Mrs. P very slowly slid her hand off my cock and moved her arm back up to the top of the seat. Thank goodness there were beach towels nearby that I used to clean up the mess.
I must admit that for several years I felt guilty about what had happened, but I wouldn't have traded that hand job with any sexual experience that I have ever had. Mrs. P and I never discussed that night, but I have used this event as a major jack off subject ever since. I have also shared this story with a couple of my lovers over the years and they said it made them get sexually excited hearing about an older woman being the first person besides myself to make me cum.