Definition - What does Contemporaneous Trader mean?
contemporaneous-trader is a trader who enters an order on the other side of the market at the same time as a trader with inside information enters an order. Contemporaneous traders can sue traders who act on inside information to recover losses.
Testopedia explains Contemporaneous Trader
If an investor in possession of non public material information enters an order for a security based on that information the investor has broken the law. An investor who trades on inside information maybe required to repay the investors with whom his order was executed. In addition to being required to repay the contemporaneous traders the investor may be subject to criminal prosecution.