A phrase analogous to rafting down a rocky river delta and referring to what is commonly known as a chubby, i.e. a male who is in a moderate state of sexual arousal; and therefore whose penis is partially, and not wholly erect.
Dude 1: "Whoa, check out that smokin' hot biddy!"
Dude 2: "I'm totally rockin' the delta for her tiggle bitties."
Dude 2: "I'm totally rockin' the delta for her tiggle bitties."
by Professor JA April 5, 2010