- get what one deserves
- punishment or reward that is considered to be what the recipient deserved
- After the supervisor was suspended, many workers felt that he got his just deserts.
- He killed my innocent bird, but got his just deserts when he was beaten by somebody for abusing.
- Our neighbor Mr. Jones got just deserts when he was left helpless in need by her wife, he never ever respected her.
- Sarah has got no sympathy for her son and husband, she got his just deserts.
1275–1325; Middle English < Old French deserte.
In fact its deserts, not desserts
The idiom is frequently reasonably written just desserts. Using just desserts is not a error, and it is much more common than just deserts in 21st-century texts.