眾生本有的性德，攝持含藏一切如來的功德，如母胎攝藏嬰兒，故稱胎藏界。

陳義孝編, 竺摩法師鑑定, 《佛學常見辭彙》

胎藏界The womb-container world (garbha-dhātu). A term usedin esoteric Buddhism to signify all-inclusiveness and fertility. See 胎藏界曼荼羅.

胎藏，梵語 garbha，音譯蘗喇婆；界，梵語 dhātu，音譯馱睹。全稱大悲胎藏生。密教兩界之一。與「金剛界」相對。胎藏有含藏覆護及攝持之義。依大日經疏卷三謂，行者初發一切智心，如識之種子，為母胎所含藏覆護，至諸根備足，尋誕生發育，習諸技藝，後施行於事業；猶如依眾生本有之理性，學大悲萬行，顯現淨心，發起方便，修治自地，自利利他，究竟圓滿，稱為大悲胎藏生。故知，胎藏乃指眾生所具之理性，而理平等之法門，稱胎藏界，與金剛界之智差別之法門相對。又胎藏界乃從果向因本覺下轉之化他門，賅約大定、大智、大悲三德，而立佛部、金剛部、蓮華部等三部之法門。〔大日經疏卷五、祕藏記〕

佛光電子大辭典

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Garbhadhātu, or Garbhakośa-(dhātu), the womb treasury, the universal source from which all things are produced; the matrix; the embryo; likened to a womb in which all of a child is conceived— its body, mind, etc. It is container and content; it covers and nourishes; and is the source of all supply. It represents the 理性 fundamental nature, both material elements and pure bodhi, or wisdom in essence or purity; 理 being the garbhadhātu as fundamental wisdom, and 智 acquired wisdom or knowledge, the vajradhātu. It also represents the human heart in its innocence or pristine purity, which is considered as the source of all Buddha-pity and moral knowledge. And it indicates that from the central being in the maṇḍala, viz. the Sun as symbol of Vairocana, there issue all the other manifestations of wisdom and power, Buddhas, bodhisattvas, demons, etc. It is 本覺 original intellect, or the static intellectuality, in contrast with 始覺 intellection, the initial or dynamic intellectuality represented in the vajradhātu; hence it is the 因 cause and vajradhātu the 果 effect; though as both are a unity, the reverse may be the rule, the effect being also the cause; it is also likened to 利他 enriching others, as vajradhātu is to 自利 enriching self. Kōbō Daishi, founder of the Yoga or Shingon 眞言 School in Japan, adopted the representation of the ideas in maṇḍalas, or diagrams, as the best way of revealing the mystic doctrine to the ignorant. The garbhadhātu is the womb or treasury of all things, the universe; the 理 fundamental principle, the source; its symbols are a triangle on its base, and an open lotus as representing the sun and Vairocana. In Japan this maṇḍala is placed on the east, typifying the rising sun as source, or 理. The vajradhātu is placed west and represents 智 wisdom or knowledge as derived from 理 the underlying principle, but the two are essential one to the other, neither existing apart. The material and spiritual; wisdom-source and intelligence; essence and substance; and similar complementary ideas are thus portrayed; the garbhadhātu may be generally considered as the static and the vajradhātu as the dynamic categories, which are nevertheless a unity. The garbhadhātu is divided into 三部 three sections representing samādhi or quiescence, wisdom-store, and pity-store, or thought, knowledge, pity; one is called the Buddha-section, the others the Vajra and Lotus sections respectively; the three also typify vimokṣa, prajñā, and dharmakāya, or freedom, understanding, and spirituality. There are three heads of these sections, i. e. Vairocana, Vajrapāṇi, and Avalokiteśvara; each has a mother or source, e. g. Vairocana from Buddha's-eye; and each has a 明王 or emanation of protection against evil; also a śakti or female energy; a germ-letter, etc. The diagram of five Buddhas contains also four bodhisattvas, making nine in all, and there are altogether thirteen 大院 or great courts of various types of ideas, of varying numbers, generally spoken of as 414. Cf. 金剛界; 大日; 兩部.

A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous