Antonyms of adv formally

1 of 2 senses of formally

Sense 2
formally -- (in a formal manner; "he was dressed rather formally")
       Antonym of informally (Sense 1)
      => informally -- (without formality; "he visited us informally")

Synonyms of adv formally

2 senses of formally

Sense 1
formally, officially -- (with official authorization; "the club will be formally recognized")

Sense 2
formally -- (in a formal manner; "he was dressed rather formally")