«زَي غَنَمِ الْعَرَبْ تِبَاتْ تِشْتَر عَلَى بَرْبُورْهَا»

The picture is of the flocks of desert-dwelling herders, not Arabs as a people, which find too little forage on sparse land to fill their bellies. At night they go on chewing the cud with nothing to show for it but the mucus running from their noses. The motion of eating continues while nourishment is absent.

Applied to people, the saying mocks someone in a miserable situation who comforts or distracts themselves with something that brings no benefit. It points to a show of coping, a pretense of having something, that leaves the person no better off than before.

Use it, usually with sarcasm, about someone who is badly off yet keeps soothing themselves with hollow excuses, empty hopes or worthless substitutes. The crude image of snot can sound insulting when aimed at a person, so it fits banter or criticism rather than polite conversation.