Meaning

noun a cgs unit of dynamic viscosity equal to one dyne-second per square centimeter; the viscosity of a fluid in which a force of one dyne per square centimeter maintains a velocity of 1 centimeter per sec

noun a state of being balanced in a stable equilibrium

noun great coolness and composure under strain

originFrom Middle English poys, poyse, from Anglo-Norman pois, Middle French pois (“weight”) and Anglo-Norman poise, Middle French poise (“measure of weight”), from Latin pendere (“to weigh, ponder, think”). Doublet of peise.

Etymology from Wiktionary, CC BY-SA 3.0