Senses
啃 to gnaw
To gnaw, nibble, or bite off something hard bit by bit using the front teeth
啃 to kiss
(slang) To kiss; to smooch.
啃 to eat
(colloquial) To eat, especially when eating heartily or consuming several items in one sitting.
啃 to study hard
(figurative) To pore over or delve into a difficult book or subject