吞食 is a verb-object compound (离合词) meaning 'to swallow' or 'to devour', often used for animals eating prey. As a separable verb, you can insert aspect markers or measure words between 吞 and 食, e.g., 吞了食 (swallowed food) or 吞过一次食 (devoured once). However, in modern Chinese it is also commonly used as a transitive verb directly followed by an object (吞食猎物).