A name, typically paired with another mildly offensive word, given to someone who you and your friends dislike. The primary reason for assigning a Deltrese nickname is so it's possible to talk shit about them whether their listening to your conversation or not.
Brianna: There goes Dusty Deltrese again; when will she ever start wearing normal clothes?
Kaleb: I don't know girl. I just don't know.
Dusty Deltrese: Who's Dusty Deltrese?
Brianna: Oh, don't worry about it. You don't know them.
This act is very similar to the act of throwing shade. Instead of just having an attitude, however, you raise a small drink umbrella (commonly found in cocktails) above the person you wish to throw shade at and reprimand them for what they have said.
Isaac: Is Queen B's new album perfect or what?
Griffin: It's okay, I guess.
Isaac: *umbrelling Griffin* You can go.