The Brief: Chonk, chonky, and chonker are terms for chubby cats that became popular online in summer 2018.

DEEP DIVE
Similar to other silly terms used to describe cute animals (like doggo),Β chonkΒ is a made-up word to classify fat cats. It is not typically used as an insult, but rather as a term of endearment.
The “Chonk Chart” is a popular meme that was originally posted to the Facebook group “THIS CAT IS C H O N K Y” by Emilie Chiang:

oh lawd he comin pic.twitter.com/jqJBZY9hlS
— ππππΆππππ πΎππππππππ (@dgahk) October 4, 2018
Internet users have also applied the term to other animals:
OH MY GOD SOMEONE MADE A RAIL CHONK CHART @RallidaeRule pic.twitter.com/1PtTDtgKzS
— Julie Blommaert π©πΌβπ¬ (@Julie_B92) October 10, 2018
In the bear world, itβs survival of the fattest. In this round of #FatBearWeek itβs 856, the areaβs most dominant bear, vs 32 Chunk.
Does dominance deliver for 856? Or is 32 Chunk a total chonk? Which titan of the tundra is the absolute unit?
Vote now: https://t.co/az5KQLICFI pic.twitter.com/8zrfMU8MbK
— Katmai National Park (@KatmaiNPS) October 6, 2018