Another form of the word, "Egotism," is really interchangeable, though in ordinary language it is often used specially (and similarly "egoism," as in George Meredith's Egoist) to describe the habit of magnifying one's self and one's achievements, or regarding all things from a selfish point of view.
The egoist and the altruist are both imperfect.
Thus the man who seeks only or primarily his own moral perfection is an egoist par excellence.
A practical theory of ethics seeks to establish a particular moral ideal; if it is an absolute criterion, then the altruist would place first the attainment of that ideal by others, while the egoist would seek it for himself.
He flattered in turn Saint Just and the Terrorists, the Thermidorians and the Directors, and played always for his own hand - a strange egoist who rose to fame as the leader of an idealist and sentimental crusade.