It's a verb that combines the words "lim" (limp) and "nalili" (a prefix that indicates a state of being or action).
Here's how you could use it:
* Nalilimping siya dahil sa sakit ng paa. (He is limping because of the pain in his foot.)
* Ang aso ay nalilimping pagkatapos ng aksidente. (The dog is limping after the accident.)
So, "nalilimping" basically means "to be limping" or "to walk with a limp".