by turn

by turns

In an alternating cycle; in successive or rotating turns. I think something was wrong, for her manner was by turns welcoming and cold, which made for a disconcerting evening. My wife and I divide household tasks by turns.
See also: by, turn
Farlex Dictionary of Idioms.

by ˈturn(s)

used when talking of contrasting feelings or actions which follow each other: He looked surprised, worried and angry by turn. When they told me I had got the job in New York, I felt by turns excited and anxious.
See also: by, turn
Farlex Partner Idioms Dictionary
See also:
  • by turns
  • turn around
  • turn around (something)
  • turn round
  • take turns
  • take turns doing something/to do something
  • take turns with
  • hooter
  • hooters
  • round robin