had been tittering

• past perfect progressive

  past perfect progressive

  Used to describe an action that was ongoing continuously in the past up until another past event interrupted it.

  of titter.
  titter

  verb (used without object)

  to laugh in a restrained, self-conscious, or affected way, as from nervousness or in ill-suppressed amusement.

More Suggestions

• child-battering
• had better
• marine engineering