性感 (xìnggǎn) is a direct, neutral adjective meaning 'sexy' — it describes someone or something that arouses sexual attraction. It's the standard word for this concept, unlike 火辣辣 (huǒ là là), which is more intense and colloquial ('hot, scorching'), or 性 (xìng), which is a suffix for abstract qualities (e.g. 可能性 'possibility').