Aikidō literally means "way (dō) to adjust (ai) your breathing, intention, and energy (ki)". (See also my Aikidō dictionary and my upcoming discussion of "ki".)
But it is linguistically problematic to separate the term's components like this, as "aiki" is an idiom with a specific meaning originating from Daitō-ryū Aiki-jūjutsu, signifying the special principle, with which to react and move in relation to an attack. Namely, to apply "aiki" on an opponent means to coordinate your movements with the direction and momentum of the attack, to add your weight and power to the attacker's, in order to disturb his center of gravity so that with "joined forces" you can throw him or bring him to the ground. For that it is necessary to adjust your own impulses of breathing, movement and power to those of your attacker, i.e. in a sense to bring yourself on the same wavelength (quite in the spirit of "good vibrations").
Because negative emotions such as antipathy towards an opponent will obstruct this method of dealing with an attack, Aikidō is often referred to, in a figurative sense, as a "way of harmony".
That does not mean, though, that you have to subject yourself to an attacker's mean intentions or to face them passively. On the contrary, you will actively step up to an attack, neutralize the danger and, if possible, show your opponent the errors of his ways.
(Author: Max Seinsch)