herm

noun

1. a monument consisting of a four-sided shaft tapering inward from top to bottom and bearing a head or bust; those of Hermes usually had an erect penis, which passersby stroked for luck.

noun plural herms, hermae (ˈhɜːmiː) or hermai (ˈhɜːmaɪ)

1. (in ancient Greece) a stone head of Hermes surmounting a square stone pillar