Irimi __Meaning: Entering or putting in the body.
Irimi (ee-ree-mee) is the second pillar of Aikido (Aikido techniques are structured around six main pillars). Irimi involves entering deeply around or behind an attack to defuse or neutralize the attack. The concept of irimi teaches one to blend with or enter into an opponent's attack to become one with the opponent's movement and leaving the opponent with nowhere to strike. This movement is utilized during the moment of your opponent's attack. To complete the movement, you move out of your opponent's line of attack to your opponent's shikaku, or blind spot. When executed properly, you can strike your opponent with great force, combining his attacking momentum and your forward movement.
The entering principle is basic to most Aikido movements as the postures and movements in Aikido contain quite a few oblique stances which are adapted from Sōjutsu (spear fighting).
In Aikido, we have numerous examples of techniques exhibiting the concepts of yin and yang. Irimi and tenkan are an example. Tenkan is the motion of turning (yin) and irimi is the motion of entering (yang).
Irimi is one of two motions Aikido students perform in the role of nage. Practicing irimi will help the Aikido student develop Hara, balance, and groundedness.
(The above quoted from Wikipedia's "Irimi" page
what are the 1st. 2nd. (Irimi) 3rd. 4th. 5th. and 6th. ? if any one know kindly help thanks.