English to English

adverb (r)

• without formality(adv.all)

  Example:
  He visited us informally.
  

  Antonym:
  formally
  

  source: wordnet30
• with the use of colloquial expressions(adv.all)

  Synonym:
  colloquially, conversationally
  

  source: wordnet30
• In an informal manner.(adverb)

  source: webster1913