Thin or non-existent lips, the opposite of the more desirable DSLs, or "dick sucking lips". This is an obvious technological reference to the advent of broadband internet, specifically Digital Subscriber Lines or DSL as it is commonly known, as opposed to the now archaic 56kbps and slower “dial-up” modems, considered obsolete and thus less desirable by most.
“I would have taken her back to the spot for some dome but I’m not down for the dial-ups.”
Generally describing an instance in which penetration is achieved in a single motion and then immediately removed. Full intercourse is thus not engaged. This term has been bastardized to include sexual contact where only the tip is inserted repeatedly for the purpose of coaxing the target into full submission. The result is either a hesitant “We should stop”, or a conceding “Ok, get a condom.” Also commonly known as "just the tip" as popularized by Vince Vaughn's character in the movie Wedding Crashers.
“I wasn’t down to fuck cuz she was jockin too hard so I just gave her a dip.”