As adjectives the difference between upmost and topmost
is that upmost is uppermost while topmost is at or nearest to the top; uppermost; being the very highest.
upmost
English
Adjective
(head)
Uppermost.
topmost
English
Adjective
(-)
at or nearest to the top; uppermost; being the very highest.
Antonyms
* bottommost
See also
* leftmost, rightmost