1. To use a pump for a particular length of time. I kept pumping for nearly 20 minutes, but I just couldn't get any breast milk out. I pumped for a minute or two, but the tire wasn't inflating, so there must be a leak in it somewhere.
2. To press on or manipulate something in an up-and-down motion for a period of time. In this usage, a noun or pronoun is used between "pump" and "for." I pumped the gas pedal for a few minutes while I tried getting the engine to start. I hate using a manual air pump to inflate these air mattresses—you have to stand there pumping it for half an hour each time!
3. To extract something using a pump for a period of time. In this usage, a noun or pronoun is used between "pump" and "for." We've been pumping water for nearly the entire, and the basement is still flooded. We've pumped oil in this region for years.
4. To use a pump for the extraction of some substance. They wanted to start pumping for oil on our land, but we told them "no." We're developing a machine that will pump for water deep beneath the Earth's crust so as to irrigate formerly arid regions.
5. To attempt to extract information from someone. In this usage, a noun or pronoun is used between "pump" and "for." The police brought the witness in and pumped him for details about the suspects. Let's pump him for information about the new project.
See also: pump
pump someone for something
Inf. to try to get information about something out of someone. The representative of the other company pumped Harry for information, but he refused to say anything. Are you trying to pump me for company secrets?
See also: pump