What is "oplomachi"

The oplomachi were a designation or possibly a class of Roman gladiator with relatively little mention in literary sources. They are often identified with the similarly named hoplomachus (a class of gladiator styled after the Greek hoplite), but literary mentions do not seem to relate the two, despite the similarity of the names. According to Justus Lipsius, an oplomachus was one of two designations of Samnite; he conjectures that Samnite variants were called oplomachi when matched against a Thracian, and a secutor when facing a retiarii. Though historical accounts identify them primarily as an opponent of the Thraex, they appear in a Pompeian list as fighting not only against Thraeces, but against Murmillones and Dimachaeri as well.