1.) The act having sex with a cactus, usually in a desert in Arizona. When the male party is about to climax, he forcibly shoves his testicles against the cactus' most sharp needles. As he ejaculates onto the cactus, he then removes his testicles.
2.) Someone who performs this act.
3.) A red penguin with large nipples.
1.) I'm so horny, I could do the cactus sack.
2.) That guy is such a cactus sack.
3.) Why does that cactus sack have such bangin' tits?