Lingam is a term used in reference to the Hindu God, Shiva. It is often used as a representation of the male penis.
Kinkly explains Lingam
The lingam is a phallic symbol used to represent the penis. It is often seen alongside the yoni which represents its female counterpart. The two symbols are often portrayed as united to represent the spiritual, creative, and sexual oneness of male and female. The symbols are frequently used in the context of tantric sex and the Kama Sutra.