His ungraceful behavior at the dinner party made everyone feel awkward.

ungraceful 是由前缀 un-（表示否定）和形容词 graceful（优雅的）组成的复合形容词。graceful 来自名词 grace（优雅）加上形容词后缀 -ful（充满...的）。ungraceful 字面意思是"不优雅的"，引申为"笨拙的、不得体的"。