Marketing Window

A deadline by which a project must be completed by, otherwise the project/product is not viable and might as well not be undertaken in the first place.

Sometimes legitimate, sometimes used as a negotiating ploy to get designers to reduce their estimates, with the corresponding expectation that they will work additional (unpaid) overtime to meet the reduced estimate.

Examples of legitimate MarketingWindows.

A contractual obligation to deliver by a certain date.
A legal requirement with a hard deadline.
Need to deliver product to meet a particular selling season (i.e. Christmas)

Examples of questionable MarketingWindows

"Marketing feels that we need it." Ask why.
"We need revenue from the project this fiscal year to meet our forecast." That may be true; but that's not the design team's problem. (At least, it shouldn't be). CountingTheChickensBeforeTheyHatch is generally unsound (but all-too-common) management practice.
"The competition is coming out with their project on that day". Usually not a hard deadline.

Remember--a MarketingWindow, to be legitimate, is a hard deadline. A good test of such a deadline is to ask what happens if the project is a day late (or a week, for some suitable short time period), vs. a day/week early. If the cost of that day is immense, far greater than the benefit of coming in a week early, you may have a hard deadline. If the cost of the day is simply one day's worth of lost orders and additional labor expense; that isn't a hard deadline.