"Greek" is often used to refer to anal sex.
Those who profess to be enthusiastic about "Greek sex" like anal sex. During "French" is used for tongue play, especially in the context of oral sex, "Greek" thus describes another popular sex practice.
Theories about why anal sex can be called "Greek" differ to some extent. What is certain, however, is that many ancient works of art show men having sex with each other. Perhaps this is where the modern term comes from? After all, the society of antiquity seemed to deal with this topic comparatively openly.
Greek also plays a role in numerous porn films nowadays, of course. There is hardly a modern flick in which the actors do not have anal sex at least once. This is true not only for gay films, but also for Straight-Porn.
If you want to make your individual anal sex a little more varied, you can use a little lubricant. This is especially recommended when using sex toys and rather large penises. The gel can not only make anal sex easier, but often also a little hornier. As is often the case, however, personal taste is the deciding factor.
Last but not least: Gays who want to pamper themselves in a Greek way can of course fall back on classics like vibrators and dildos in many variations.