1. To be a possible threat or danger or to create a problem for other people: Ray's dangerous driving behaviors were posing a threat to the safety of other drivers and even to pedestrians.

The park officials figured that the excessive number of demonstrators posed a threat of destruction and excessive littering of trash in the city park.

2. To raise questions or challenges: Larry's mother has often posed the question as to what he was planning to do with his life after he graduated from high school.
3. Pretending to be someone or something in order to deceive other people: Shirley's sister posed as an underaged student in order to get free admission to the museum.

The undercover police officers were posing as drug dealers so they could arrest those who were actually involved with selling illegal drugs.