(1) A bug tent is the place you dump your least favorite hiking companions, in hopes that overnight they will eat each other so you no longer have to hear them, see them, or deal with the idiot things they do to bug you all day. Or if not that, you hope that hordes of wild insects will take care of them for you. And sometimes that works out.
(2) A bug tent is a doll-sized tent to accommodate your pet cockroach Tina, so she can come backpacking with you. Which is what you've always wanted. Because that's the kind of person you are. Kind. And creepy. Which is why your trail name is Bugger. Which is yet another reason why everyone keeps far, far, far away from you. Far.
(3) A bug tent is a refuge from the most ravenous, persistent, and least predictable predators out there, most of which can fly, and all of which have more legs than you do, and use them to run ever so fast, and show ferocious persistence in homing in on your tasty, deliciously-salted flesh.
Typically, this sort of tent is just like a regular tent but without a rain fly, and consists of mesh strung over a frame. And it may be a regular tent from which you have temporarily removed the rain fly.
It can also be a frameless but well-architected mesh bag hanging under a tarp or a purpose-made job fitting inside a single-walled tarp tent. Mostly these meshy things are used for overnight sleeps on clear nights, but can also serve as places to eat meals safe from the nippy ones.
On slow days some people enjoy sitting inside their bug tents and pulling the little probing mosquito beaks off the heads of those critters as they relentlessly poke and poke through the mesh, hungry for blood.
(4) The last refuge for the bug-crazed, i.e., backpackers.
As always, Effort or Eff it. No sniveling.
Source: How to talk in the woods.