When you do something spontaneously, you do it on a whim, without preparing for it or giving it much thought. If your math teacher spontaneously breaks into a tap dance, it will surprise the whole class.

Spontaneously belting out a song on the subway is very different from practicing over many weeks for a choral concert solo. Things that happen spontaneously aren't planned: improvisation in music or theater, for example, happens spontaneously. Spontaneously comes from the adjective spontaneous, with its Late Latin root spontaneus, "willing," or "of one's free will."

Definitions of spontaneously
  1. adverb
    in a spontaneous manner
    “this shift occurs spontaneously
  2. adverb
    without advance preparation
Word Family