"Put someone on the spot" is an expression used when someone is suddenly asked a direct or uncomfortable question, which puts them in a difficult situation. It could also refer to the act of making someone feel embarrassed or humiliated in public. Some synonyms for "put someone on the spot" include to challenge, to grill, to confront, to pressure, to test, to question, to interrogate, to cross-examine, to make demands, to provoke or to embarrass. These synonyms can be used interchangeably depending on the context of the situation and the intensity of the pressure that the person feels.