dagger
Word family noundaggerboarddagger
Weapons
dag·ger /ˈdæɡə $ -ər/ noun [countableC] 1. 
PMWa short pointed knife used as a weapon 匕首，短剑
PMWa short pointed knife used as a weapon 匕首，短剑2. look daggers at somebody informalLOOK AT to look at someone angrily 对某人怒目而视
Examples from the Corpus
look daggers at somebody• The lady behind the counter looked daggers at me.• Their relationship is not free and easy but at least Red is no longer looking daggers at her.
3. be at daggers drawn ANGRYif two people are at daggers drawn, they are extremely angry with each other 势不两立，剑拔弩张
→ cloak-and-daggerExamples from the Corpus
be at daggers drawn• The prospect of an interesting friendship had been destroyed and now they were at daggers drawn.• In practice they are at daggers drawn as the furore over Tom Clarke's pronouncements on the subject this week amply illustrates.
Examples from the Corpus
dagger• Even though she'd expected it, that smile twisted in Shannon's heart like a dagger.• Caterina takes a dagger from the gallery artifact collection and goes to meet him.• The two combatants were armed with spears and shields, and each man had sword and dagger at his belt.• It was rather like having a heated dagger thrust into the eyeball and twisted, then caustic soda rubbed in the wound.• Their relationship is not free and easy but at least Red is no longer looking daggers at her.• I jumped to one side, and the dagger went deep into my shoulder.• As the dagger went in, the bush turned grey and all its thorns went pale and soft.
(1300-1400) Perhaps from dag “to push a knife into” ((14-18 centuries))