Definitions:

1. below cost adverb
   • At a loss for words, I watched as my girlfriend sobbed in her mother's arms, wondering why my life had taken such a tragic turn.
2. filled with bewilderment adjective
   • At a loss for words, I watched as my girlfriend sobbed in her mother's arms, wondering why my life had taken such a tragic turn.
3. filled with bewilderment adjective
   • At a loss to understand why he had been passed over for the promotion, John resigned from his job.

Synonyms:

• nonplused
• nonplussed
• puzzled