having a wrong idea of what is likely to happen or of what you can really do; not based on facts

I think these sales forecasts are unrealistic, considering how slow sales are at present. 考虑到目前的销售速度有多慢，我觉得这些销售预测是不切实际的。

[ + to infinitive ] It's unrealistic to expect an answer before next week. 期待下周之前得到答复是不现实的。