This is just a rough guestimate, but I believe that I’ve heard “guestimate” said five times in the past two weeks. If you ask me, that’s six times too many–if you count the time I just said it.
I’m not going to debate whether guestimate (or guestimation) is a word since I’m sure that some descriptivists out there would find it listed in some dictionary or would simply argue that its use is all that’s needed to make it word, so I’ll focus, instead, on the lack of logic of its usage.
Guestimate is clearly a combination of the word guess and estimate, most likely a humorous concoction by a clever person in the 20th century, and the lack of logic arises from the fact that the word estimate means “an approximate judgement,” which means that it’s a conclusion drawn without complete evidence. A guess is to “arrive a conclusion without having complete knowledge.”
In other words, a guess and an estimate are effectively the same thing, so the words don’t need to be combined; they need to be separated–separated into different sentences since pairing them is a redundancy.
I know. I know. I’ve heard it argued that a guestimate is a less precise estimate than an estimate but more precise than a guess. That’s what I call I stretch, or a stretchtimation of language.