a large jar or pail for collecting household slop for disposal.
Origin of slop jar
First recorded in 1850–55
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for slop jar
Then I dropped the vinaigrette in the slop-jar and jumped down from the wash-stand.The Story of Dago|Annie Fellows-Johnston