That guy at the party was such a weirdo, just playing with his phone in the corner all night.

weirdo 是由形容词 weird（奇怪的、怪异的）加上名词后缀 -o 构成的名词，指"行为古怪的人"。这个后缀 -o 常用于口语中，将形容词转化为名词，带有轻微贬义或调侃意味。