Synonyms of spontaneously

2 Syllables
freely, ad-lib
3 Syllables
instanter, impromptu, artlessly, instantly
4 Syllables
informally, optionally, naturally, unconsciously
5 Syllables
voluntarily, immediately, instantaneously, unreservedly, impulsively, unaffectedly, unpretentiously
6 Syllables
automatically, extemporaneously
7 Syllables
characteristically