In short: dukkha means suffering, or unsatisfactoriness. It covers everything from pain and grief to the quiet sense that nothing lasting can be held. It is the first of the Four Noble Truths: something to understand, not to fear.
☸ The Buddha's definition
"Rebirth is suffering; old age is suffering; illness is suffering; death is suffering; being coupled with the disliked is suffering; separation from the liked is suffering; not getting what you wish for is suffering."
SN 56.11 · The Four Noble Truths
Pain
Change
Conditions
The three marks · All terms · 3 minutes of practice
Questions people ask
What does dukkha mean?
Dukkha is usually translated 'suffering'. It covers pain and grief, but also the subtle unsatisfactoriness of anything that changes. It is the first of the Four Noble Truths (SN 56.11).