Question

what is a feasibility study

Answer 1

In essence the title describes what it is. It is a study (usually a paper or 'desk top' study) to determine if a project is viable. This can range from a 'back of the envelope' calculation of costs to a very detailed look at everything ranging from the political climate to environmental considerations.

The phrase "feasibility study" also refers to the outcome fo the activity which is usually a report.

see:

http://en.wikipedia.org/wiki/Feasibility_study