unceremonious

释义：本意是和ceremonious相对表示事情是“非正式的”，但在留学文书里也常常引申用来体现“突然的、狼狈的”。

例句：
Jacob King performs an unceremonious dismount during a recent rodeo.
A romantic relationship takes an unceremonious nose dive and you wind up in love's great landfill.