Another form of the ever popular, "circle jerk", where there are only two participants therefore forming a "line" instead of a "circle".
The two participants jerk-off together and when they have both completed the action, they have attained a "linear jerk". Although sometimes referred to as a "linear wank", in the United States it has been growing in popularity in dorm rooms everwhere under the term "linear jerk".
Eric and I were in our dorm room, and it was just us, so we did a linear jerk. Next time you should come and we can have a circle jerk!