Today's Parola del Giorno is the noun expression, la promessa da marinàio, which means unfulfilled promise or worthless promise.
This expression refers to promises we make in difficult situations but then never fulfill those promises, like when we bargain with a higher power during a dangerous situation but then fail to fulfill those promises when the danger or problem has passed.
This expression pops up a lot on blogs and in articles when they discuss politicians and their inability to keep promises.
You can read about the history of this expression here.
See the expression used below:
Non posso garantire la mia presenza alla tua seduta di laurea, non faccio promesse da marinaio. Se mi danno il giorno libero a lavoro ci sarò sicuramente ma posso fartelo sapere venerdì prossimo.
I cannot guarantee I’ll be at your graduation, I do not make worthless promises. If they give me the day off work, I will surely be there but I can let you know next Friday.