The phrase "sucking action" refers to the act of drawing in or pulling something towards you using the force created by sucking or inhaling. Full definition
• Breastfeeding for at least one year has been associated with better oral development due to the unique sucking action required with nursing at the breast. (motherandchildhealth.com)
These pumps provide sucking action very similar to your breastfeeding baby, so the action should be pain - free. (newkidscenter.com)
Let - down occurs when the baby's sucking action on the breast sends a message to the brain. (lansinoh.com)