“Entrainment” is not an everyday word, but it’s a term used in various fields of science. It can describe the phenomenon of one organism rhythmically and internally adjusting itself to another. It’s when life-pulses coordinate.
Fireflies lighting up in synchronization has been described as entrainment. Jazz musicians locking in together is, in its way, entrainment.
Ben Ratliff defining "entrainment" and how it features prominently in Van Morrison's new release "Keep It Simple" (due out 1 April), in today's New York Times' piece: Van Morrison on Science, the Spiritual and Rituals.