to drink: to take liquid in through the mouth
This is the ordinary Hebrew word for drinking, the everyday counterpart of eating. Most of its uses are plainly literal: people and animals drink water, wine, milk, or whatever is at hand, and a thirsty person who cannot find water is in real danger. Because food and drink belong together, the word constantly pairs with eating, and that pairing slides easily into the larger idea of sitting down to a meal or a celebration.
From there the same word reaches into the world of feasting. A wedding, a homecoming, a treaty, or a royal court is described as people eating and drinking, and the heavier end of that range shades into carousing and drunkenness, where the drinking itself is the point and the occasion is one of excess.
The prophets and poets then take this concrete act and turn it into a vivid picture of receiving what is handed to you. To drink the cup is to take in full measure of whatever the cup holds, most often God's anger and judgment, but also reeling confusion, suffering, or even the violence and wrongdoing a wicked person swallows as readily as water. The act is the same throughout, taking something in through the mouth; what changes is what is being taken in and why.