Stopping.
Mountain ☶ means stopping in the proper place, getting rid of incorrect enjoyment and improper action. – Liu Yiming, The Taoist I Ching, Hexagram #5 Making a Young Girl Marry
Mountain represents stopping, stillness. In the body of the hexagram, one yang rests on top of two yins: The yang is above, the yin is below; yang governs yin and yin obeys yang, so the celestial is not damaged by the mundane., Inwardly still and outwardly still, one stops inside and also stops outside. Because one stillness pervades inside and outside, it is called Mountain.
– Liu Yiming, The Taoist I Ching, Hexagram #52 Mountain
"The trigram Mountain ☶ refers to stillness, stopping. In the primordial (前天 - before Heaven) arrangement of the eight trigrams it represents stillness that enables the celestial to manifest itself."
http:// www.taoistiching.org/mountain.html