| An approximation based on some amount of known information. Commonly used in estimates for duration, cost, or difficulty of technological projects.
This is NOT simply a made-up quantity. That would be a guess. Nor is it an educated guess. That concept differs from guesstimate by its lack of plausibility and/or accuracy. For some reason, appending "-timate" to "guess" is more reassuring than "guess" alone, or even coupled with "educated".
I'm confused by this rather sprained logic, but I guesstimate that it will take another few years before the definitions acquire a semblance of rationality. | 
