'at a loss' definitions:

Definition of 'at a loss'

(from WordNet)
adverb
Below cost; "sold the car at a loss"
adjective
Filled with bewilderment; "at a loss to understand those remarks"; "puzzled that she left without saying goodbye" [syn: at a loss(p), nonplused, nonplussed, puzzled]

Synonyms of 'at a loss'

From: Moby Thesaurus