Definition from Wiktionary, the free dictionary
gnaw + -er
gnawer (plural gnawers)
- A rodent or other similar type of animal that gnaws.
- 1839, Charles Darwin, The Voyage of the Beagle, Chapter 7, 
- South America is characterized by possessing many peculiar gnawers […] .
- 1947, Lloyd Glenn Ingles, Mammals of California, Stanford University Press, p. 182, 
- The Norway Rat is a good digger and a superb gnawer.
rodent or other similar type of animal that gnaws