AT A LOSS

Puzzled, perplexed, embarrassed, staggered, posed, nonplussed, aground, ashore, stranded, cornered, out, at one's wits' end, hard pressed, hard up, at a stand, in doubt, in difficulty, put to it, put to one's trumps, put to one's shifts, out of one's depth, beyond one's depth, in a quandary, at fault, in a dilemma, not knowing what to do.