e·qui·lib·ri·um n., pl. e·qui·lib·ri·ums or e·qui·lib·ri·a .
1. A condition in which all acting influences are canceled by others, resulting in a stable, balanced, or unchanging system.
2. Mental or emotional balance; poise.
The opposite of the equilibrium, may I add, is Koyaanisqatsi, which is a Hopi Indian word, meaning "life without balance". It's also a title of the first of the Qatsi trilogy by a young filmmaker (at the time, 1983) Godfrey Reggio. Watch it, it may change the way you view your life. The film has no actors, no script, no dialogues, just images and a brilliant score by Philip Glass.