/ə'pɒn; ə`pɑn/
prep
1 (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.

prep formal
[Date: 1100-1200; Origin: up + on]
used to mean 'on' or 'onto'
　an honour bestowed upon the association
　We are completely dependent upon your help.
　Brandon threw him upon the ground.
if a time or event is upon you, it is about to happen
　Winter is almost upon us.
layer upon layer/mile upon mile etc
used to emphasize that there are a lot of layers, miles etc
　mile upon mile of golden sand
→once upon a timeatonce¹ (14)
→take it upon yourself to do sthattake¹ (27)