Definition - What does Dirty Bit mean?
Dirty bit is a colloquial name for a specific bit in computer memory that traditional computing systems use to indicate a modification or write-to. Although there is not much information on the origin of this term, one could understand the concept of the dirty bit being a temporary place marker that will eventually be erased.
A dirty bit is also known as a modified bit.
Techopedia explains Dirty Bit
For certain kinds of modifications, a computing system adds a dirty bit in memory. Dirty bits can also be used as markers in memory for specific processes. After they have served their purpose in indicating something like a modification or marking unprocessed data, algorithms or other tools often remove the dirty bit from memory. In essence, the dirty bit is a temporary spot on computing memory to represent some function or condition.