Something that's tolerable is something you're able to live with. The best thing you can say about sleeping in a tent with your younger siblings might be that it's tolerable.
If you can tolerate something, or put up with it, it's tolerable. You can also use this adjective to mean "good enough" or "adequate." If your waiter asks how your meal is and you answer, "The pizza is tolerable," you're not giving a rave review; you're basically saying, "It's average" or "It's edible, but nothing special." Tolerable comes from the Latin tolerabilis, "that may be endured."