If you describe someone as excitable, you mean that they behave in a rather nervous way and become excited very easily.
例句
Mary sat beside Elaine, who today seemed excitable...玛丽坐在伊莱恩身边,伊莱恩今天似乎有些激动。The staff were somewhat alarmed by the man, who was in an excitable state.那个情绪激动的男人让职员们感到有些恐慌。