維基辭典YuePhrase
Original phonetic: /piːn³³ faː³³ mou̯²¹ sœːŋ²¹/
irregular, fickle, capricious
Examples
這兒的天氣變化無常，剛才還是清空萬里，現在卻已經鳥雲密佈了。
The weather here is fickle; just now, it was clear skies for miles, but now it's already densely covered in birds and clouds.