shadowboxing

/SH AE1 D OW0 B AA1 K S IH0 NG/
verb
  1. 1

    To practice moves without an actual opponent, often in front of a mirror.

noun
  1. 1

    A form of solo exercise, involving throwing punches at the air, and not at an opponent.

Source: https://en.wiktionary.org/wiki/shadowbox, https://en.wiktionary.org/wiki/shadowboxing