Hard to define, but I was thinking along the lines of taking advantage of the other party, perhaps through means that are (or should be) illegal. A few examples:

- Baiting a prospective employee with lies about the earning/advancement potential [illegal]

- Pressuring an employee to perform work off the clock (this is often done by setting performance standards that are unattainable without overtime work, while simultaneously "forbidding" overtime) [illegal]

- Using information you know about an employee (such as their inability to switch jobs because of personal circumstances) to low-ball their pay [not illegal, just sleazy]

- Manipulating the circumstances around incentive-based pay so that the employee performs the incentivized work but doesn't end up qualifying for the bonus [illegal, depending]

- Interfering with an employee's career growth/marketability so they won't be able to command higher pay [not illegal, just sleazy]

Edit: I suppose the theme here is seeking to capture more of the value of someone's labor in ways that undermine their ability to negotiate the best deal for themselves. It undermines the whole idea of people freely negotiating for a mutually beneficial relationship.