If you're talking about this report, it looks to me like it does contain a clear definition of "schemer" in section 1.1.3, pg. 25: 

It’s easy to see why terminally valuing reward-on-the-episode would lead to training-gaming (since training-gaming just is: optimizing for reward-on-the-episode). But what about instrumental training-gaming? Why would reward-on-the-episode be a good instrumental goal?

In principle, this could happen in various ways. Maybe, for example, the AI wants the humans who designed it to get raises, and it knows that getting high reward on the episode will cause this, so it training-games for this reason.

The most common story, though, is that getting reward-on-the-episode is a good instrumental strategy for getting power—either for the AI itself, or for some other AIs (and power is useful for a very wide variety of goals). I’ll call AIs that are training-gaming for this reason “power-motivated instrumental training-gamers,” or “schemers” for short.

By this definition, a human would be considered a schemer if they gamed something analogous to a training process in order to gain power. For example, if a company tries to instill loyalty in its employees, an employee who professes loyalty insincerely as a means to a promotion would be considered a schemer (as I understand it).