(idiomatic) A challenge with the odds of success stacked strongly against.

(transitive) To disapprove of.

The upsilon particle

(physics) Any of a number of bound states of a heavy quark and its antiquark, especially that formed from a bottom quark and an anti-bottom quark.

The uppermost side of anything

plural of upper side

(informal) someone or something which gives up

Alternative form of put upon

Imposed on, taken advantage of, used, taken for granted, or unappreciated.

A social and economic class lying above the lower middle class and below the upper class.