Aspiration has two meanings in medicine describing either the drawing in of a fluid with the sucking motion or the drawing out of a fluid with a suction. The first usage commonly describes the accidental ingestion of a fluid or solid into the trachea (windpipe) and lungs.

Aspiration pneumonia is a condition where there is an infection of the lungs caused by the ingestion of food, liquids, alcohol, or any other substance entering the windpipe and lodging in the lungs. This is more common in people who are given general anesthesia, intake of excess alcohol, aged people, and in conditions like Parkinson's disease, and multiple sclerosis. It can be prevented by, avoiding excess alcohol intake, coughing out the food items to prevent them from entering into the lungs, sitting in an upright position while having food, chewing the food slowly and completely, and avoiding nicotine intake. If there is any problem in the food pipe or pain while swallowing, then immediate medical attention is required.

Aspiration may also refer to the extraction of fluids using a needle and syringe or other suctioning devices. The medical technique has dual purposes. It may be used to remove excessive or harmful fluids from the body. The aspirated fluid can then be sent to a pathology laboratory for analysis. Fluid can build up inside the body for many reasons.

Doctors define pulmonary aspiration as accidentally inhaling an object or fluid into the airways. It can lead to coughing, difficulty breathing, discomfort, and sometimes choking. In some cases, pneumonia can develop. Most people occasionally experience pulmonary aspiration when something they are eating or drinking “goes down the wrong way.”