Short-form of "upload" that is often used as a hashtag on social media posts to indicate that the user posting the content is the originator of the content and that they are not simply retweeting or reblogging the item.
Here's a photo of a whale #upl
The constant state of "pre-ejaculation" by those who are always consuming porn to get in the mood to masturbate (and may be dealing with a wet tip from precum).
She's hot. That's some good prejac content right there.