priapus

Pronunciation: \prī-ˈā-pəs\ (listen to it on m-w.com)

Noun: a Greek and Roman god of gardens and male generative power; phallus; phallic in shape; something lewd or obscene (definition on dictionary.com)

Etymology: 14th century; Latin, Greek.

Usage: Lots of Google books results. Here's a quote from On the Road (Penguin 20th Century Classics):

He wrote of Dean as a "child of the rainbow" who bore his torment in his agonized priapus. (pp 47-48)