When your mind and body becomes so overwhelmed with such ecstatic joy while delivering the father of the groom speech that you yell out at the end "I'm having a mental ejaculation of joy" and then drop the mic.
When someone jumps the gun during an attempt to synchronize cracking open cans of soda or beer... therefore ruining the massive head-turning "clack" sound you were all hoping to create.
question: "Dude! what happened there? We were going to crack-open on the count of 3"
response: "Sorry man... I've been having trouble with premature eclackulation lately"
Jack failed to ejaculate during sex with Jill but successfully came afterward while eating a bowl of cereal in a phenomenon known as post mature ejaculation.
when a zach just puts "it" in just a lil bit and cums prematurely , thus resulting in Plan B
Khloe: Last night Zach just put it in a little bit and still came really early, I need to go grab some plan B
Chasette: Aw damn girl sounds like your man got a case of premature ezachulation :(