nonplus

“For Greeks, the pillars marked the end of the known world. The Romans said the pillars were inscribed with a Latin warning—” “Nonplus ultra,” Percy said.

But at times some extremely artless animadversions are heard that almost nonplus us.

The young lord, thus abandoned, looked at first at a nonplus, and seemed for a while more than half-inclined to follow.

And the gold"--he paused and seemed to be at a nonplus--"I'm afraid 'twould take too long to count it.

Nonplus, non′plus, n. a state in which no more can be done or said: great difficulty.—v.t. to perplex completely, to puzzle:—pr.p. non′plussing; pa.t. and pa.p. non′plussed.