1. To pull someone or something downward and into something as due to a current of water or the force of gravity. A noun or pronoun can be used between "suck" and "down." The drain sucked down all the water from the bath. Be careful—the current out there can suck you down in a split second.

2. To drink something very quickly or hastily. A noun or pronoun can be used between "suck" and "down." You need to stop sucking down those beers, or you're going to be wasted by 9 o'clock! Let me just suck this coffee down before we leave.

3. To form a seal (on someone or something) due to the force of a vacuum. A noun or pronoun can be used between "suck" and "down." As the heated contents cool, the air is driven out and the lid sucks down on the rim of the jar, forming an airtight seal. When an octopus flexes certain muscles, it causes suckers on its arms to suck down on whatever (or whomever) it is trying to grasp.