Saunf means: An Indian culinary and everyday term for fennel seeds , widely used across South Asian cooking and as a mouth freshener. In Hindi, Urdu, and related languages, 'saunf' refers both to the fennel plant. It is mainly Indian English and may not be understood outside that context. It carries sexual or vulgar connotations; not alarming on its own but worth understanding the context your teen heard it in. This is a food-related word and harmless in itself.