If you describe someone as excitable, you mean that they behave in a rather nervous way and become excited very easily.
Mary sat beside Elaine, who today seemed excitable.
The staff were somewhat alarmed by the man, who was in an excitable state.
Synonyms: nervous, emotional, violent, sensitive
excitability (ɪksaɪtəbɪlɪti ) uncountable noun She has always been inclined to excitability.
Synonyms: nervousness, stress, tension, volatility