Yes Boss is a secret achievement/trophy in Deus Ex: Human Revolution. It is earned by persuading David Sarif to give you information about the breach in the firewall that led to the attack on Sarif Industries.
This has to be done after you come back from the FEMA facility in Highland Park. You will be asked to debrief David Sarif. Before you can do that, however, Pritchard will ask to see you in your office.
When you go to Pritchard, he will tell you that he has discovered a security breach in the company's firewall, and will tell you to ask David Sarif about it.
When you go up to Sarif's office, Jensen will confront David Sarif about this installed security breach, and Sarif will get defensive. The conversation path used to force David to give out more information about the breach is random as conversation options change each time you play through. What may have worked for someone else might not work for you.
If you have the C.A.S.I.E Social Enhancement Augmentation, then just use pheromones to achieve the desired result. Sarif's personality type is Alpha, so choose the Appease option.
You'll know if you're successful in convincing him, when Sarif tells you what the security breach is concerned about. The achievement should pop soon after this.