of a sudden

Related to of a sudden: all of a sudden, sudden infant death syndrome

all of a sudden

Unexpectedly and abruptly; suddenly. I was startled when the fire alarm went off all of a sudden. I thought Laura and I were friends, but all of a sudden, she stopped talking to me.
See also: all, of, sudden
Farlex Dictionary of Idioms.

(all) of a sudden

suddenly.
As a noun sudden is now found only in this phrase, but from the mid 16th century to the early 18th century it was in regular use in the sense ‘an unexpected danger or emergency’.
See also: of, sudden
Farlex Partner Idioms Dictionary
See also:
  • all of a sudden
  • have a (sudden) rush of blood to the head
  • have a rush of blood to the head
  • a (sudden) rush of blood (to the head)
  • a rush of blood
  • sudden
  • have a wild hair to (do something)
  • get a wild hair to (do something)
  • alarm
  • alarm bell