What is papañca?

One word in Pali Canon seems to be especially challenging for translators to convey. This word is "*papañca*" (e.g. MN18 , DN21 , Sn 4.11 , AN4.173 ). Some attempts at translating *papañca* include "exaggeration", "proliferation ", "association ", "conceptualization ", "objectification ", and "reification ". What is *papañca* and what is it's significance in Buddhism? How is it used in Pali Canon and what is it's referent in real life? How is *papañca* (*prapañca* in Sanskrit) explained by Mahayana philosophers such as Nagarjuna, Asanga, and Tsongkhapa?