n.不严肃，轻浮
Merriam-Webster Online Dictionary
levity (noun)1.
excessive or unseemly frivolity
2.
lack of steadiness - changeableness
Merriam-Webster Online Thesaurus
levity (noun)a lack of seriousness often at an improper time
SYNONYMS:
facetiousness, flightiness, flippancy, frivolousness, frothiness, levity, light-headedness, light-mindedness, lightness, sillinessRELATED WORDS:
cheer, cheerfulness, festivity, gaiety ( gayety), glee, gleefulness, high-spiritedness, hilarity, joviality, lightheartedness, merriment, mirth, mirthfulness; childishness, goofiness, puerilityNEAR ANTONYMS:
dejection, depression, despondency, dispiritedness, downheartedness, gloom, gloominess, heartsickness, joylessness, melancholy, mopes, moroseness, sadness, sullenness, unhappiness