Source : Webster's Revised Unabridged Dictionary (1913)

Informally \In*form"al*ly\, adv.
   In an informal manner.

Source : WordNet®

informally
     adv 1: without formality; "he visited us informally" [syn: {without
            formality}] [ant: {formally}]
     2: with the use of colloquial expressions; "this building is
        colloquially referred to as The Barn" [syn: {colloquially},
         {conversationally}]
     3: in a causal way; at home; "we'll have dinner en famille"
        [syn: {en famille}]