To excite someone in a mild, teasing way — and in modern English, usually in a sexual way. A photograph, a story, a piece of gossip, or a newspaper headline titillates: it gives the reader a small thrill, hints at something, and stops short of showing it. That holding-back is the heart of the word. Something fully explicit does not titillate; something that suggests does. The word usually carries a judgement. When people say a film 'titillates' rather than tells a story, they mean it is cheap, that it is working on the audience's body instead of their mind. It is formal-sounding — a reviewer's or a journalist's word, not something friends say to each other. There is an older, non-sexual sense, still alive in careful writing, where it simply means to tickle or to pleasantly stimulate: an unusual dish can titillate the taste buds. That use is fine and clean, but the sexual meaning is now so strong that many readers hear it anyway.