'Informally' definitions:

Definition of 'informally'

(from WordNet)
adverb
Without formality; "he visited us informally" [ant: formally]
adverb
With the use of colloquial expressions; "this building is colloquially referred to as The Barn" [syn: colloquially, conversationally, informally]

Definition of 'Informally'

From: GCIDE
  • Informally \In*form"al*ly\, adv. In an informal manner. [1913 Webster]