Discreet: If left on a table it is not obvious what it is or what it is for. If you are caught using it red handed it is not possible initially to know that it contains weed. The see through screen on MFLB prevents this and thus not making it "discreet" for use in public.
Weak: After vaping a full trench it might get you through a second full trench but from my own experience once it hit about 75% of the second the battery got weak and the indicator light started to fade heavily. Not weak would be getting through at least 3 full trenches with some power to spare. I found myself charging more often than vaping with the MFLB.
Flimsy: Instead of clicking a button to power it on it requires manually pressing the battery which therefore only lets you use it in limited ways. You can't use it without pressing the battery. It is flimsy because the battery isn't part of the device and could fall out and in most cases you would carry them separately in the pocket. Not flimsy would be an integrated solution.
Each to their own of course but these are the definitions you sought
Nothing wrong with your definitions. Okay, maybe you could find a better word than "flimsy" but I quibble. Mine vary, that's why I asked. The LB suits my needs but it doesn't suit yours, which is why there is no best vapourizer.