There are several synonyms that can be used instead of "ply with questions," depending on the context and tone of the conversation. One possible synonym is "interrogate," which implies a more aggressive or intense questioning style. Another option is "probe," which suggests a more investigative or exploratory approach to questioning. A third synonym could be "grill," which indicates a more confrontational or hostile interaction. Other possible synonyms could include "question intensely," "ask relentlessly," or "dig for information." Ultimately, the choice of synonym will depend on the desired effect and the specific circumstances of the situation.