hand-wavy

handwavy and hand-wavy {of a demonstration, proof, argument, or explanation} (unexplained, unfounded; almost magical in origin; missing important details or logical steps, perhaps instead appealing to common sense, tradition, intuition, or examples) — из пальца высосанный, шитый белыми нитками, взятый с потолка; на коленке сделанный (контекст); (=бездоказательный, не основанный на фактах или логике)

.......You’re being a little hand-wavy with your explanation here. —
Look, man... Just because I haven't filled in details doesn't mean I'm being hand wavy.

.......Of course I'm being hand-wavy and the devil is the details, but you get the idea.

.......McWilliams' article consists similarly of a lot of hand-wavy arguments that appeal to "common sense", but I don't think applying "common sense" to a system as complex as food production is sufficient.

.......I know this seems kind of hand-wavy, but bear with me and I'll show you in a minute where it comes from.

.......My personal feeling was Jacobson didn't seem as strong because his side felt more hand-wavy, but that could be my bias.

Why is it so important to know what it is that makes a human different from all the other animals?

hand-waving

It is certainly useful to think about the similarities between us and other animals (insofar as that prompts us to have a little more humility as a species). I suppose that one could do some hand-waving and come up with something useful about thinking about what is unique about us as a species. Mostly, it just seems to be an irresistibly interesting thing to think about, simply for it’s own sake. (Robert Sapolsky)

Origin
The adjective "hand-wavy" comes from a reference to a magician's act where he waves his hands and makes something (a bird, bouquet, handkerchief, etc.) appear as if out of thin air. The words 'hand' and 'wave' are compounded (from the phrase "I'll wave my hands and (something) will appear" or something similar) and then an adjective suffix "-y" is affixed to change the inflection to create "hand-wavy". It is generally used to describe an idea or concept that doesn't seem to have any foundation, that seems to appear "out of thin air". It is typically used by professors, TA's and students (anyone involved in the learning process) since they have the most contact with these novel ideas. It probably first came about due to its rather "magical" connotation to describe how "magically" some of these laws or concepts first appear. (neologisms.rice.edu)

Related vocabulary:
[высосать из пальца]
[шито белыми нитками]
[брать с потолка]
[far-fetched]
[hand-wavy]