upon/əˈpɔn; ə`pɑn/ prep1 (fml 文) = on2 1, 4b, 9, 10, 13.2 (idm 习语) once upon a time => once. (almost) u`pon him, them, us, etc (of a time in the future) rapidly approaching （指将来的某一时刻）迅速接近 Christmas is almost upon us again. 圣诞节又快到了.
牛津英汉双解词典