1. The act of evaluating or appraising or slapping together a loose proposal when you really ar not sure about it at all.
2. To calculate/guess roughly (the amount, extent, magnitude, position, or value of something).
3. Providing significatn room or 'fudge factor' for irregularities.
Well if you could Roughtimate how long its going to take and how much its goig to cost and then let me know.