In the Theosophist era of Buddhism the word enlightenment was used as a translation of Buddhist nirvana, bringing with it European connotations of rationality, humanist philosophy, and so forth. In the hippie era the Japanese word satori came into prominence as its replacement, thanks mainly to D.T. Suzuki and the Beats.
Hippies tended to use satori to mean the form of enlightenment conveyed in Zen koans where one is shaken out of one's skin by a mind-blowing idea or a confusing action that adheres to no normal understanding of reality. Of course, this lends itself to taking a lot of LSD and achieving some temporary satori.
Today enlightenment has come back into favor with Western Buddhists; the original Pali nibbana may also sometimes be used.