Synonyms for Once in a while:

• adv

  •at times (adverb)
  • intermittently.
  •every now and then (adverb)
  • ever so often,
  • sometimes.

• adv.

  •every now and then (adverb)
  • every now then.
  •from time to time (adverb)
  • from time time.
  •rarely (adverb)
  • extra,
  • extremely,
  • notably,
  • uncommon,
  • little,
  • barely,
  • remarkably,
  • unusually.
  •seldom (adverb)
  • whimsically,
  • in a few cases,
  • scarcely,
  • inhabitually,
  • a few times,
  • Semioccasionally,
  • not very often.
  •sometimes (adverb)
  • consistently,
  • ever and again,
  • constantly,
  • frequently.

• n.

  •
  • seldom.
  •at times (noun)
  • at times.

• Other synonyms:

  •
  • seasonal.
  •from time to time
  • from time to time.
  •rarely
  • blue.