unreliable
🇺🇸
/ˌʌnrɪˈlaɪəbl/
🇬🇧
/ˌʌnrɪˈlaɪəbl/
not able to be trusted or depended on
The weather forecast is often unreliable, so it's best to be prepared for rain even if it says sunny.
天気予報はしばしば信頼できないので、晴れと言っていても雨に備えておくのが最善です。