The term Kangeiko means training of martial arts or geigoto (accomplishment) conducted in mid-winter season. By carrying out training while enduring coldness, it aims not only to improve skills but also to discipline one's mind.
It is conducted during the coldest time of day, before dawn or at dawn. Under the current social/daily life situation, it refers to the trainings conducted around the time of daikan (one of the twenty-four divisions of four seasons, and the coldest period in winter). As Shinto religion, Shugendo (Japanese mountain asceticism) and some sects of Buddhism incorporate ascetic practices like bathing in the sea/river or standing under a waterfall, called kanshugyo or kangyo, with the aim of mental training, Kangeiko of budo often incorporate such exercises. One of Budo's main purpose is to overcome one's weakness (self-governing) as well as to pave the way for the future by driving one's body/mind to an extreme situation. Also, Kangeiko is one of the few vanishing characteristics of budo.
It is used as kigo (season words) for haiku (Japanese seventeen-syllable poem).