A Sloppy Dallas is a sexual phrase, which means giving head while having dip(tobacco) in the lip. Usually meant for the pure redneck/hillbilly people looking to get it on.
A blowjob where the giver has a lip packed with dip so the dip juice gets on the shaft. Popularized by The Goons. Typically seen in hillbilly communities.
"Yeah my cousin gave me a Sloppy Dallas last night."
"Oh nice did she use Copenhagen."