What is the meaning of well-nigh?

adverb

• Of actions or states. ( slightly short of or not quite accomplished; all but)
  • usage: "the job is (just) about done"; "the baby was almost asleep when the alarm sounded"; "we're almost finished"; "the car all but ran her down"; "he nearly fainted"; "talked for nigh onto 2 hours"; "the recording is well-nigh perfect"; "virtually all the parties signed the contract"; "I was near exhausted by the run"; "most everyone agrees"
  • synonyms: about, almost, most, nearly, near, nigh, virtually