The lingam (also linga, ling, Shiva linga, Shiv ling, Sanskrit: liṅgaṃ, meaning "mark", "sign", or "inference") is a representation of the Hindu deity Shiva used for worship in temples. In traditional Indian society, the linga is rather seen as a symbol of the energy and potential of God, Shiva himself.
The lingam is often represented alongside the yoni(Sanskirt word, literally "vagina" or "womb), a symbol of the goddess or of Shakti, female creative energy. The union of lingam and yoni represents the "indivisible two-in-oneness of male and female, the passive space and active time from which all life originates".
The Sanskrit term liṅgaṃ, transliterated as linga, means, ‘Penis’. Shiva Lingum, therefore means Penis of Lord Shiva and is therefore considered most sacred by Shaivaites sect of Hindus.
Example via www.ramdass.org: "Om Namah Sivaya"