What is Lame Duck?

Legal Definition
A lame duck, in politics, is an elected official whose successor has already been elected. The official is often seen as having less influence with other politicians due to their limited time left in office. Conversely, a lame duck is free to make decisions that exercise their standard powers with little fear of consequence, such as issuing executive orders, pardons, or other controversial edicts. Lame duck politicians result from term limits, planned retirement, or electoral losses.
-- Wikipedia
Legal Definition
A cant term on the stock exchange for a person unable to meet his engagements.
-- Black's Law Dictionary