To gobble something up; to finish eating all of something quickly and easily (colloquial).
子どもがパンケーキをペロリと平らげた。
The child polished off the pancakes in no time.
彼は大盛りのカレーをペロリと平らげてしまった。
He cleared a large serving of curry without difficulty.
試食で出たケーキをみんながペロリと平らげた。
Everyone quickly devoured the sample cakes.