So I began to look beyond the forums to other sources online. Invariably I found 13 instead of 8 basic taiji movements, and because I am a total beginner I assumed that this was from another family line or something. It wasn't until I found this Wikipedia entry on tuishou that I realized that what we call "eight basic movements" are the Eight Gates which, along with the Five Steps, created the 13 basic movements I saw mentioned everywhere.
From the Wikipedia Article:
Would we consider this definition (which is given for all Chinese internal martial arts) suitable for a basic understanding of the Eight Gates and Five Steps as it pertains to Yang Family CMC/Michuan practice?The Eight Gates (八門 bā mén):
P'eng (掤, py péng) - An upward circular movement, forward or backward, yielding or offsetting usually with the arms to disrupt the opponent's centre of gravity, often translated as "Ward Off." Peng is also described more subtly as an energetic quality that should be present in every taiji movement as a part of the concept of "song" (鬆) -- or relaxation -- providing alertness, the strength to maintain structure when pressed, and absence of muscular tension in the body.
Lü (履, lǜ) - A sideways, circular yielding movement, often translated as "Roll Back."
Chi (擠 (simpl.: 挤), jǐ) - A pressing or squeezing offset in a direction away from the body, usually done with the back of the hand or outside edge of the forearm. Chi is often translated as "Press."
An (按, àn) - To offset with the hand, usually a slight lift up with the fingers then a push down with the palm, which can appear as a strike if done quickly. Often translated as "Push."
Tsai (採, cǎi) - To pluck or pick downwards with the hand, especially with the fingertips or palm. The word tsai is part of the compound that means to gather, collect or pluck a tea leaf from a branch (採茶, cǎi chá). Often translated "Pluck" or "Grasp."
Lieh (挒, liè) - Lieh means to separate, to twist or to offset with a spiral motion, often while making immobile another part of the body (such as a hand or leg) to split an opponent's body thereby destroying posture and balance. Lieh is often translated as "Split."
Chou (肘, zhǒu) - To strike or push with the elbow. Usually translated as "Elbow Strike" or "Elbow Stroke" or just plain "Elbow."
K'ao (靠, kào) - To strike or push with the shoulder or upper back. The word k'ao implies leaning or inclining. Usually translated "Shoulder Strike," "Shoulder Stroke" or "Shoulder."
The Five Steps (五步 wǔ bù):
Chin Pu (進步 jìn bù) - Forward step.
T'ui Pu (退步 tùi bù) - Backward step.
Tsuo Ku (左顧 (simpl.: 左顾) zǔo gù) - Left step.
You P'an (右盼 yòu pàn) - Right step.
Chung Ting (中定 zhōng dìng) - The central position, balance, equilibrium. Not just the physical center, but a condition which is expected to be present at all times in the first four steps as well, associated with the concept of rooting (the stability said to be achieved by a correctly aligned, thoroughly relaxed body as a result of correct Tai Chi training). Chung ting can also be compared to the Taoist concept of moderation or the Buddhist "middle way" as discouraging extremes of behavior, or in this case, movement. An extreme of movement, usually characterized as leaning to one side or the other, destroys a practitioner's balance and enables defeat.
The Eight Gates are said to be associated with the eight trigrams (Bagua 八卦 bā guà) of the I Ching, the Five Steps with the five elements of the Taoist Wu Hsing (五行 wǔ xíng); metal, water, wood, fire, and earth. Collectively they are sometimes referred to as the "Thirteen Postures of T'ai Chi Chuan" and their combinations and permutations are cataloged more or less exhaustively in the different styles of solo forms which Tai Chi is mostly known for by the general public. Pushing hands is practiced so that students have an opportunity for "hands-on" experience of the theoretical implications of the solo forms. Traditional internal teachers say that just training solo forms isn't enough to learn a martial art; that without the pushing hands, reflex and sensitivity to another's movements and intent are lost. Each component is seen as equally necessary, yin and yang, for realizing the health, meditative, and self-defense applications.