A quick drawing of a cock and balls which you perform on your classmate's notes when they fall asleep / aren't paying attention in class.
Can also be used as a verb, as in the act of speed penising.
"Check out how many speed penises we got on Phil's notebook while he was in the bathroom."
"Wow, you got speed penised bad, bro."
The unfortunately shrivelled penis that results from taking amphetamine.
Fancy a shag? Oh no, speed penis...