Source : Webster's Revised Unabridged Dictionary (1913)

Excitability \Ex*cit"a*bil"i*ty\, n. [Cf. F. excitabilit['e].]
   1. The quality of being readily excited; proneness to be
      affected by exciting causes.

   2. (Physiol.) The property manifested by living organisms,
      and the elements and tissues of which they are
      constituted, of responding to the action of stimulants;
      irritability; as, nervous excitability.

Source : WordNet®

excitability
     n 1: excessive sensitivity of an organ or body part [syn: {irritability}]
     2: being easily excited [syn: {excitableness}, {volatility}]