In a teamwork situation, an extremely irrational person, who takes charge of a project through sheer force of will rather than competence and leads it in a direction which guarantees failure.
Background: The Don Quixote of literature had a tendency to do extraordinarily stupid things without thinking them through. But people were loathe to try and stop him on account of his being a few cans short of a six pack.
I am officially referring to my project leader as "Don Quixote" from this point on. She's got the idea in her head that she, rather than the boss, defines the project KPIs. I'm going along with it because a good performance appraisal is not worth the next few months of my life being made a living hell by that crazy-ass bitch!