sucking
v.v. to pull liquid or air into your mouth using your lips and tongue. You might do this when drinking through a straw or eating a piece of candy.
v. drawing liquid, air, or an object into the mouth by creating a vacuum through the motion of the lips and tongue. Often used in a continuous form to describe a habitual or ongoing action.
The baby is sucking on a pacifier.
The child sat quietly on the porch, sucking a cold juice box through a plastic straw to beat the summer heat.
By sucking the venom from the wound, the protagonist in the film demonstrated a classic, though medically discouraged, response to a snake bite.
The verb is transitive when taking an object like 'a straw' or 'a sweet', but often functions intransitively with the preposition 'on'.