one-at-a-time rule
nounUK /wʌn æt ə taɪm ruːl/
US /wʌn æt ə taɪm rul/
A rule that says you do only one thing at a time.
The teacher used the one-at-a-time rule so everyone got a turn on the swing.
OTHER MEANINGS
2. A guideline in computing that processes or handles items one by one rather than all together.
The program follows a one-at-a-time rule when printing the files.
3. A classroom or group policy that lets only one person speak or act at any moment.
During show-and-tell, the one-at-a-time rule keeps the room calm.
4. A personal habit of focusing on a single task before starting another.
She follows the one-at-a-time rule to finish her homework without mistakes.