She became defensive when her opinions were questioned.

defensive 是形容词，由动词 defend（防御、保护）加上后缀 -ive 构成。defend 来自拉丁语 defendere，由 de-（表示"远离"）和 fendere（"打击"）组成，字面意思是"击退攻击"。defensive 表示"防御性的、戒备的"，形容人在感到被批评或威胁时采取的保护性态度。