Definition: energetic and dynamic; indefatigable

• I seem to have tireless energy when I get involved in things, which is a good way to do things because if you’re gonna do something, you’d better make sure you do it well. — James (Jimmy) Patrick Page (1944-) English musician
• Labor is work that leaves no trace behind it when it is finished, or if it does, as in the case of the tilled field, this product of human activity requires still more labor, incessant, tireless labor, to maintain its identity as a ‘work’ of man. — Mary Therese McCarthy (1912–1989) American novelist