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...瑪麗坐在伊萊恩身邊，伊萊恩今天似乎有些激動。The staff were somewhat alarmed by the man, who was in an excitable state.那個情緒激動的男人讓職員們感到有些恐慌。