Upon

Preposition

up and on; upward so as to get or be on

He climbed upon his horse and rode off.

in an elevated position on

There is a television antenna upon every house in the neighborhood.

in or into complete or approximate contact with, as an attacker or an important or pressing occasion

The enemy was upon us and our soldiers had little time to escape. The Christmas holiday will soon be upon us and we have hardly begun to buy gifts. The time to take action is upon us.

immediately or very soon after

She went into mourning upon her husband's death.

on the occasion of

She was joyful upon seeing her child take his first steps.

on (in any of various senses, used as an equivalent of on with no added idea of ascent or elevation, and preferred in certain cases only for euphonic or metrical reasons)

He swore upon his honor as a gentleman.

Synonyms

preposition

about , above , against , astride , atop , concerning , onto , over , stop , thereafter