四字熟語 [よじじゅくご] – four-character idiomatic compound

• 四 [シ・よ・よん] – four
• 字 [ジ・あざ] – character
• 熟 [ジュク・うれる] – ripen; mature
• 語 [ゴ・かたる] – word; language

As you can see, an idiom is a “matured/ripened word.”  四字熟語 are among my favorite things in Japanese.  In the future, I intend to bring more 四字熟語 to your attention, but in the meantime, here are a few examples:

一日千秋 [いちじつせんしゅう] – One-Day-Thousand-Autumn - To wait impatiently; each moment seeming like an eternity.

七転八起 [ななころびやおき・しちてんはっき] – Seven-Fall-Eight-Rise – Always picking oneself up despite repeated failures.

以心伝心 [いしんでんしん] – By Means Of-Heart-Transmit-Heart - telepathy; direct heart-to-heart communication

一期一会 [いちごいちえ] – One-Time-One-Meeting – a once-in-a-lifetime encounter.  (Interestingly, “Forrest Gump” was titled 一期一会 in Japan.)