To suck means to pull something in through your mouth by creating a vacuum, like when you draw lemonade up through a straw. Your mouth creates lower air pressure inside, and the higher pressure outside pushes the liquid up. You might suck on a popsicle, suck the juice from an orange slice, or suck air through your teeth when something surprises you.

Many animals use sucking as their primary way of eating. Baby mammals suck milk from their mothers. Butterflies and hummingbirds suck nectar from flowers through their long, tube-like mouths. Even vacuum cleaners work by sucking: they create low pressure inside that pulls in air and dirt.

The word appears in some useful expressions too. When something sucks you in, it captures your attention completely, like an exciting book that makes you lose track of time. Getting sucked into an argument means becoming involved in it even when you didn't want to be.