"Mouth movements" refers to the way a person's mouth moves while speaking or making certain sounds. It includes how the lips, tongue, and jaw move to produce different words or expressions. Full definition
A baby's jaw, tongue, and mouth movements when sucking on these are different and if your baby uses the same action at the breast this can cause nipple soreness. (breastfeedingtoday-llli.org)
This can happen when baby has not had the opportunity to establish the correct mouth movements needed for breastfeeding and develops a preference for an artificial nipple. (lansinoh.com)
We'll also be adding some cinematic mouth movement as well! (kickstarter.com)