IPA: /ˈsnæpɪʃnəs/
KK: /ˈsnæpɪʃnəs/
The quality of being irritable or quick to respond in a sharp manner.
Her snappishness made it difficult for her friends to approach her when she was upset.
Snappishness is formed from "snappish" (from the verb "snap", meaning to make a sudden, sharp noise or to speak abruptly) and "-ness" (a suffix used to form nouns indicating a state or quality). The word describes the quality of being irritable or quick to speak sharply.
Think of someone who speaks abruptly or makes a sudden noise ('snap') — the '-ness' indicates the state of being that way, so snappishness means the quality of being irritable.