the mind > mental capacity > belief > uncertainty, doubt, hesitation > perplexity, bewilderment > [adjective] > at a loss (8)
Disgraced, lost, ruined; stupefied.
Brought to a nonplus or standstill; at a nonplus; perplexed, confounded.
Unable to reply. Obsolete.
Utterly puzzled; confounded, nonplussed.