There are many synonyms for the term "dusty smile," which can be used to describe a facial expression that is dry, stale, and lacking in enthusiasm. Some alternatives to "dusty smile" include a wooden grin, a lackluster smile, a forced smile, or a faint smile. Other options might include a weak smile, a half-hearted smile, or a barely-there smile. Each of these phrases can help convey the idea that the person in question is not genuinely happy or excited, but is instead putting on a superficial or insincere expression. Depending on the context, any of these synonyms might be more appropriate than "dusty smile" to communicate a specific tone or emotion.