(一脸) + 得意 + 的 + 样子
The adjective 得意 (déyì) means "smug," "proud," or "pleased with oneself." It describes a self-satisfied attitude, often used to portray someone showing off or feeling triumphant, as in 一脸得意的样子 (a smug look).
他考了第一名,一脸得意的表情。
tā kǎo le dì yī míng, yī liǎn déyì de biǎoqíng.
He got first place on the exam, with a smug expression on his face.
她得意地笑了笑,什么也没说。
tā déyì de xiào le xiào, shénme yě méi shuō.
She smiled smugly and said nothing.
别那么得意,下次可不一定赢。
bié nàme déyì, xià cì kě bù yīdìng yíng.
Don't be so smug — you won't necessarily win next time.