Refers to food or a preparation from which you want to remove the liquid part, such as the cooking water.
Example: "Drain beans after cooking"
Meaning: Separate the beans from their cooking water, first by removing them from the pan with a skimmer or spider, then or directly by pouring them into a colander.
Remarks: A colander is the most practical utensil, but you can also use a salad spinner, depending on what you need to drain.