The term is not really a project management term. In any case, the best thing to address this issue is to allow team members to estimate their own tasks, and then the project manager will add the appropriate contingency. If the project manager estimates the same level of effort and productivity across the board based on the oldest/newest resource, then the project can be either way behind schedule or way ahead of schedule.
New team members (e.g. new to the company) are extremely tricky, since the estimates that they give cannot be verified with their previous work. In this scenario, the project manager typically add a lot of contingency and asks the team manager to do the estimates for them.