Translation

不安定な / 変わりやすい / 揮発性の

Meaning

Volatile means likely to change suddenly or become dangerous, especially a situation, market, or person's mood. It is about instability, not talkativeness; that word is voluble.

Examples

• 選挙前は市場が非常に不安定になりました。
  The market became highly volatile before the election.
• 彼は怒りやすく、職場の雰囲気を不安定にします。
  He has a volatile temper that unsettles the office.