Final answer:
The most pessimistic outcome of a task is referred to as the worst-case estimate (W). It represents the most negative results that could happen, as opposed to the best-case or probable-case estimates.
Step-by-step explanation:
The pessimistic outcome of a task is the most negative consequence that could occur if things go wrong. This is known in project management and estimation techniques as the worst-case estimate (W). In contrast, the best-case estimate (B) represents the most positive outcome, and the probable-case estimate (P) is what is most likely to happen under normal conditions. The concept of pessimistic outcomes often relates to probabilities where there's a chance of success (denoted by 'p') and a chance of failure (denoted by 'q'), with the sum of these probabilities equaling 1.