indefatigable

The word "indefatigable" describes someone or something that seems almost impossible to tire out. It usually points to steady effort over time, not just a short burst of energy. A person described this way keeps working, helping, searching, building, or pushing forward without seeming worn down. In many cases, "tireless" is the closest everyday synonym, but "indefatigable" often sounds stronger and more admiring.

You will often see it used for people with unusual dedication: an indefatigable campaigner, an indefatigable journalist, an indefatigable organizer, or an indefatigable parent caring for a family through hard times. It can also describe work or activity itself, such as indefatigable efforts to solve a problem or indefatigable support for a cause. Sometimes it is even used for things like machines or systems that keep operating without pause, though it is most often used for people.

The idea is not only physical stamina. Someone can be mentally or emotionally indefatigable too, staying focused, patient, and active through setbacks, long hours, or repeated failure. The word usually carries praise. It suggests not just effort, but admirable persistence.

So when you meet someone who keeps going, keeps helping, or keeps fighting for a goal even when the work is long and draining, "indefatigable" is a strong word for that kind of lasting energy and commitment.