What is the meaning of Grex?

A multicellular aggregate of amoeba.

A kind of group used in horticultural nomenclature, applied to the progeny of an artificial cross from specified parents, in particular for orchids.

a group of smaller animals: a flock , a pack , a swarm , etc.

a similar group of other things

a group of people: a crowd, a clique, a company, a band, a troop, etc.

a team of charioteers.

a troupe of actors.

Source: wiktionary.org