Meaning:

lucky, propitious, auspicious

Origin:

神座（“口”）上面摆着举行隆重仪式时用的礼器——圭，表示有喜庆的事。后来圭形变成了“士”，意思就不明显了。“吉”的本义是好、幸运的。

Sacrificed vessels, or “圭,” would sit atop a sacred base, or “口,” during grand ceremonies. Hence, this character represents a happy thing. Later, “圭” changed into “士,” and its meaning became opaque. The original meaning of “吉” is good and lucky.

Words:

   吉祥物 (jíxiángwù): mascot

   吉他    (jítā): guitar

   吉日   (írì): lucky day

   吉星  (jíxīng): lucky star

   吉祥  (jíxiáng): lucky, propitious, auspicious

Examples:

1. 北京奥运会的吉祥物是什么？

    Běijīng AoYùnHuì de jíxiángwù shì shénme

    What is the mascot for Beijing Olympics?

2. 中国人结婚都喜欢找个吉日。

    ZhōngGuórén jiéhūn dōu xǐhuan zhǎo ge jírì

    Chinese people prefer to marry on an auspicious day.