1. A reference to having mental or emotional stability or composure; especially, under tension or strain; calmness; equilibrium: Sometimes it is very difficult for a teacher to be equanimous during a lesson when the students have to be reminded not to talk so often.
2. Relating to being calm and in control of the emotions; primarily in a difficult situation: Jane was quite equanimous, or self-possessed, when being told by the authorities that she had violated the law by parking in the hospital driveway; especially, since it wasn't her car!