The word grill has two main meanings:

1. A metal frame used for cooking food over direct heat, usually from charcoal or gas flames below. When you grill hamburgers or vegetables, you're cooking them on this frame so they get those distinctive dark lines and a slightly smoky flavor. Grilling happens at high heat, which sears the outside of the food quickly. People grill at backyard barbecues, camping trips, and restaurants. The word can be a noun (the cooking device itself) or a verb (the act of cooking on it).
2. To question someone intensely and persistently, often in an uncomfortable way. When a teacher grills a student about a missing assignment, she's asking pointed questions that demand clear answers. Police detectives might grill a suspect, asking the same questions from different angles to check if the story holds up. Parents might grill their teenager about where they were after school. When someone says “my parents really grilled me about my grades,” they mean the questions felt hot and relentless, not casual or easy to dodge.