埋頭苦幹

1. • to bury oneself in work (idiom) to be engrossed in work
2. • to make an all-out effort
3. • up to the neck in work

Character by character

• 埋(mái)bury
• 頭(tóu)head
• 苦(kǔ)bitter
• 幹(gàn)tree trunk