I'm pretty much thinking of the definition from the 1913 edition of Websters: "Suf"fer*ing, n. The bearing of pain, inconvenience, or loss; pain endured; distress, loss, or injury incurred; as, sufferings by pain or sorrow; sufferings by want or by wrongs."
For example, if everything was known and easy, wouldn't we be completely bored? Is boredom not also suffering?