The Collaborative International Dictionary of English v.0.48:
march equinox \march equinox\ n. The vernal equinox. [WordNet 1.5]WordNet (r) 3.0 (2006):
March equinox n 1: March 21 [syn: vernal equinox, March equinox, spring equinox] [ant: September equinox, autumnal equinox, fall equinox]