Greek sex is a euphemism for anal sex. Ancient Greeks were accepting of romantic or sexual relationships between males. However, anal sex was not a universally accepted practice outside of Greece, and was therefore the target of jokes in Roman comedies and plays. Romans often used Greek settings and characters as the backdrop for explicit acts of anal intercourse, indicating that the Romans may have considered anal sex to be specific to Greek culture.
More About Greek Sex
Ancient Greek language had no words for "homosexual" and "heterosexual." There was no concept in ancient Greece equivalent to the modern notion of sexual preference. A person was assumed to experience both homo- and heterosexual feelings at different times. Romantic love and sexual passion were considered normal and healthy, particularly between male partners. For this reason, certain sexual acts that are commonly defined as either "homosexual" or "heterosexual" today were, among the Greeks, simply sexual acts.